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Stockholders' Equity (Deficit) - Preferred Stock (Details)	1 Months Ended
	Jun. 30, 2017 Vote $ / shares shares	Dec. 31, 2019 $ / shares	Dec. 31, 2018 $ / shares
Stockholders' Equity (Deficit)
Preferred stock, par value (in dollars per share)		$ 0.0001	$ 0.0001
Series A Convertible Preferred Stock
Stockholders' Equity (Deficit)
Preferred stock, par value (in dollars per share)	$ 0.0001
Preferred stock conversion ratio \| shares	1
Preferred shares number voting rights \| Vote	0

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 46,697	$ 57,379
Marketable securities	392,348	426,339
Prepaid expenses and other current assets	1,152	1,483
Total current assets	440,197	485,201
Property and equipment, net	1,184	227
Right-of-use asset	675
Total assets	442,056	485,428
Current liabilities:
Accounts payable	1,178	2,487
Accrued expenses	23,637	5,957
Lease liability	315
Total current liabilities	25,130	8,444
Long-term liabilities:
Lease liability	361
Total long term liabilities	361
Total liabilities	25,491	8,444
Stockholders' equity:
referred stock, par value $0.0001 per share authorized: 5,000,000 shares at December 31, 2019 and December 31, 2018; 1,969,797 shares issued and outstanding at December 31, 2019 and December 31, 2018
Common stock, par value $0.0001 per share authorized: 200,000,000 at December 31, 2019 and December 31, 2018; 15,429,154 and 15,409,023 shares issued and outstanding at December 31, 2019 and December 31, 2018, respectively	2	2
Additional paid-in-capital	639,567	616,573
Accumulated other comprehensive gain (loss)	216	(319)
Accumulated deficit	(223,220)	(139,272)
Total stockholders' equity	416,565	476,984
Total liabilities and stockholders' equity	$ 442,056	$ 485,428

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net Loss	$ (83,948)	$ (32,811)	$ (31,154)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities	535	(288)	(56)
Comprehensive loss	$ (83,413)	$ (33,099)	$ (31,210)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Organization, Business and Basis of Presentation	12 Months Ended
Organization, Business and Basis of Presentation	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Business and Basis of Presentation	1. Organization, Business and Basis of Presentation Organization and Business Madrigal Pharmaceuticals, Inc. (the “Company” or “Madrigal”) is a clinical-stage pharmaceutical company developing novel, high-quality, small-molecule drugs addressing major unmet needs in cardiovascular, metabolic, and liver diseases. The Company’s lead compound, MGL-3196 (resmetirom), is being advanced for non-alcoholic steatohepatitis (“NASH”), a liver disease that commonly affects people with metabolic diseases such as obesity and diabetes, and non-alcoholic fatty liver disease (“NAFLD”). The Company initiated a Phase 2 study of resmetirom in NASH in October 2016. In February 2017, the Company initiated a Phase 2 study of resmetirom in patients with Heterozygous Familial Hypercholesterolemia (“HeFH”). Both Phase 2 studies were fully enrolled in 2017, the HeFH study was completed in February 2018, and the NASH study was completed in May 2018. The Company initiated two Phase 3 studies of resmetirom in NASH in 2019. Madrigal was originally incorporated as a private company (“Private Madrigal”) on August 19, 2011 and operations commenced in September 2011. On July 22, 2016, Private Madrigal completed a reverse merger (the “Merger”) into Synta Pharmaceuticals Corp. (“Synta”). Upon the consummation of the Merger, the historical financial statements of Private Madrigal became the Company’s historical financial statements.

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Liabilities
Unrealized gains on investments	$ 62
Total Deferred Tax Liabilities	62
Deferred Tax Assets
Charitable Contributions	15	$ 13	$ 4
Accrued Expenses	759	498	421
Intangibles	983	477	579
Stock Compensation	10,943	4,395	605
Property, Plant & Equipment	13	9
Unrealized Loss on Investment		92	9
Net Operating Losses	17,635	14,851	9,229
Capitalized R&D	29,364	15,108	8,671
R&D Credit	6,141	3,505	1,901
Total deferred tax assets before valuation allowance	65,853	38,948	21,419
Valuation Allowance	(65,791)	$ (38,948)	$ (21,419)
Total deferred tax assets	$ 62

Leases

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Leases

8. Leases

In 2019, the Company entered into an operating lease for office space. As described within Note 2, we adopted ASU

2016-02,

“Leases,” on January 1, 2019 requiring, among other changes, operating and finance leases with terms exceeding twelve months to be recognized as

a right-of-use asset (or “

ROU

”)

and lease liabilities on the balance sheet. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at the commencement date. The lease term is determined to be the

non-cancelable

period including any lessee renewal options that are considered reasonably certain of exercise. The interest rate implicit in lease contracts is typically not readily determinable. As such, the Company used judgment to determine an appropriate incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term in a similar economic environment.

Future minimum payments under the Company’s operating leases related to the ROU asset and lease liability as of December 31, 2019 was as follows (in thousand):


	Operating Leases
2020	$	363
2021		371
2022		31
Thereafter		—

Total minimum payments	$	765
Less: imputed interest		89

Present value of lease liabilities	$	676

As of December 31, 2019, the weighted average remaining operating lease term was 2.0 years and the weighted average discount rate used to determine the operating lease liabilities was 5.5%.

Cash paid related to the lease liability was $297 thousand for the year ended December 31, 2019.

Operating lease costs during the year ended December 31, 2019

was $386 thousand. Rent expense during the year ended December 31

2018 and 2017 was $239 thousand and $134

thousand

, respectively.

Short term and variable leases costs were immaterial during the years ended December 31, 2019, 2018 and 2017.

Leases (Tables)

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Schedule of future minimum payments for operating leases

Future minimum payments under the Company’s operating leases related to the ROU asset and lease liability as of December 31, 2019 was as follows (in thousand):


	Operating Leases
2020	$	363
2021		371
2022		31
Thereafter		—

Total minimum payments	$	765
Less: imputed interest		89

Present value of lease liabilities	$	676

Commitments and Contingencies (Details) - USD ($)	12 Months Ended
Commitments and Contingencies (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Commitments and Contingencies
Licensed product sales	$ 0	$ 0	$ 0
Research, Development and Commercialization Agreement \| Hoffmann-La Roche ("Roche")
Commitments and Contingencies
Remainder of future milestone payments	8,000,000
Milestone payment	$ 2,000,000

Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Summary of stock option activity

The following table summarizes stock option activity during the twelve months ended December 31, 2019:


	Shares			Weighted average exercise price		Weighted average remaining contractual life (years)		Aggregate intrinsic value (in thousands)
Outstanding at January 1, 2019		1,132,618		$	48.52
Options granted		378,500			118.70
Options exercised		(20,131	)		11.67
Options cancelled		(29,000	)		175.78

Outstanding at December 31, 2019		1,461,987		$	64.67		7.37	$	68,604

Exercisable at December 31, 2019		943,399		$	40.38		6.94	$	63,995

Summary of unvested restricted share activity

The following table summarizes restricted share activity during the year ended December 31, 2019:


	Shares			Weighted average exercise price
Outstanding at January 1, 2019		52,063		$	9.45
Vested		(52,063	)		9.45

Outstanding at December 31, 2019		—		$	—

Schedule of stock-based compensation expense

Stock-based compensation expense during the years ended December 31, 2019, 2018 and 2017 was as follows (in thousands):


	Years Ended December 31,
	2019		2018		2017
Stock-based compensation expense by type of award:
Stock options	$	22,487	$	12,997	$	2,662
Restricted stock		272		492		592

Total stock-based compensation expense	$	22,759	$	13,489	$	3,254

Effect of stock-based compensation expense by line item:
Research and development	$	8,277	$	3,707	$	883
General and administrative		14,482		9,782		2,371

Total stock-based compensation expense included in net loss	$	22,759	$	13,489	$	3,254

Income Taxes - Effective Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective income tax rate reconciliation
Tax benefit at U.S. federal statutory rate	$ (17,629)	$ (6,890)	$ (10,592)
Stock based compensation	(47)	(3,415)	138
Effect of tax reform, change in federal tax rate			9,260
Other nondeductible expenses	14		1
State income taxes benefit before valuation allowance, net of federal benefit	(6,613)	(5,460)	(704)
Increase in domestic valuation allowance	26,843	17,529	2,880
Research and development credit	(2,636)	(1,604)	(825)
Other adjustments	$ 68	$ (160)	$ (158)

Income Taxes - Research and Development Carryforward (Details) $ in Millions	Dec. 31, 2019 USD ($)
Federal \| Research and development carryforward
Income Taxes
Research and development tax credit carryforwards	$ 5.9

Quarterly Financial Data (unaudited)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data (unaudited)

11. Quarterly Financial Data (unaudited)

The following tables present a summary of quarterly results of operations for 2019 and 2018 (in thousands, except shares and per share data):


	Three months ended
	March 31, 2019			June 30, 2019			September 30, 2019			December 31, 2019
	March 31, 2019			June 30, 2019			September 30, 2019			December 31, 2019
Revenues:
Total revenues	$	—		$	—		$	—		$	—
Operating expenses:
Research and development		12,373			15,594			19,447			24,910
General and administrative		5,746			7,110			4,748			5,044

Total operating expenses		18,119			22,704			24,195			29,954

Loss from operations		(18,119	)		(22,704	)		(24,195	)		(29,954	)
Interest income		3,039			3,005			2,766			2,214
Other income		—			—			—			—

Net loss	$	(15,080	)	$	(19,699	)	$	(21,429	)	$	(27,740	)

Net loss per common share:
Basic and diluted net loss per common share	$	(0.98	)	$	(1.28	)	$	(1.39	)	$	(1.80	)
Basic and diluted weighted average number of common shares outstanding		15,364,465			15,368,986			15,415,096			15,429,154


	Three months ended
	March 31, 2018			June 30, 2018			September 30, 2018			December 31, 2018
	March 31, 2018			June 30, 2018			September 30, 2018			December 31, 2018
Revenues:
Total revenues	$	—		$	—		$	—		$	—
Operating expenses:
Research and development		5,198			5,109			6,211			8,871
General and administrative		1,871			2,717			5,122			5,583

Total operating expenses		7,069			7,826			11,333			14,454

Loss from operations		(7,069	)		(7,826	)		(11,333	)		(14,454	)
Interest income		705			1,166			2,821			2,979
Other income		—			200			—			—

Net loss	$	(6,364	)	$	(6,460	)	$	(8,512	)	$	(11,475	)

Net loss per common share:
Basic and diluted net loss per common share	$	(0.45	)	$	(0.45	)	$	(0.56	)	$	(0.75	)
Basic and diluted weighted average number of common shares outstanding		14,127,868			14,383,720			15,307,872			15,348,358

Income Taxes - Valuation Allowance and Uncertain Tax Position (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Income Tax Disclosure [Abstract]
Increase in valuation allowance	$ 26.8
Liability for uncertain tax positions	0.0
Income tax related interest and penalties	$ 0.0

Stockholders' Equity (Deficit)	12 Months Ended
Stockholders' Equity (Deficit)	Dec. 31, 2019
Stockholders' Equity Note [Abstract]
Stockholders' Equity (Deficit)	6. Stockholders’ Equity (Deficit) Common Stock Each common stockholder is entitled to one vote for each share of common stock held. The common stock will vote together with all other classes and series of stock of the Company as a single class on all actions to be taken by the Company’s stockholders. Each share of common stock is entitled to receive dividends, as and when declared by the Company’s board of directors. The Company has never declared cash dividends on its common stock and does not expect to do so in the foreseeable future. Preferred Stock The Series A Preferred Stock has a par value of $0.0001 per share and is convertible into shares of the common stock at a one-to-one ratio, subject to adjustment as provided in the Certificate of Designation of Preferences, Rights and Limitations of Series A Convertible Preferred Stock, that the Company filed with the Secretary of State of the State of Delaware on June 21, 2017 (the “Series A Certificate”). The terms of the Series A Preferred Stock are set forth in the Series A Certificate. Each share of the Series A Preferred Stock is convertible into shares of Common Stock following notice that may be given at the holder’s option. Upon any liquidation, dissolution or winding-up of the Company, whether voluntary or involuntary, after the satisfaction in full of the debts of the Company and the payment of any liquidation preference owed to the holders of shares of capital stock of the Company ranking prior to the Series A Preferred Stock upon liquidation, the holders of the Series A Preferred Stock shall participate pari passu with the holders of the Common Stock (on an as-if-converted-to -Common-Stock basis) in the net assets of the Company. Shares of the Series A Preferred Stock will generally have no voting rights, except as required by law. Shares of the Series A Preferred Stock will be entitled to receive dividends before shares of any other class or series of capital stock of the Company (other than dividends in the form of the Common Stock) equal to the dividend payable on each share of the Common Stock, on an as-converted basis. June 2018 Registered Offering of Common Stock In June 2018, the Company entered into an underwriting agreement with Goldman Sachs & Co. LLC, as representative of the several underwriters named therein (the “June 2018 Underwriters”), relating to an underwritten public offering (the “June 2018 Offering”) of 1,079,580 shares of the Company’s common stock, including 95,973 shares of the Company’s common stock purchased by the June 2018 Underwriters pursuant to a 30-day option to purchase such additional shares granted therein, at a public offering price of $305.00 per share. The June 2018 Offering resulted in gross proceeds to the Company of approximately $329.3 million, and net proceeds to the Company of approximately $311.8 million, after deducting the June 2018 Underwriters’ discount and other offering costs. The June 2018 Offering closed on June 11, 2018. December 2017 Registered Offering of Common Stock In December 2017, the Company entered into an underwriting agreement (the “Underwriting Agreement”) with Goldman Sachs & Co. LLC, as representative of the several underwriters named therein (the “Underwriters”), relating to an underwritten public offering (the “December 2017 Offering”) of 1,731,929 shares of the Company’s common stock, including 225,904 shares of the Company’s common stock purchased by the Underwriters pursuant to a 30-day option to purchase such additional shares granted therein, at a public offering price of $83.00 per share. The December 2017 Offering resulted in gross proceeds to the Company of approximately $143.8 million, and net proceeds to the Company of approximately $135.7 million, after deducting the Underwriters’ discount and other estimated offering expenses payable by the Company. The December 2017 Offering closed on December 21, 2017. June 2017 Private Placement Offering and Series A Convertible Preferred Stock In June 2017, the Company entered into a Securities Purchase Agreement (the “Purchase Agreement)” with a group of institutional accredited investors, who were existing, non-controlling stockholders of the Company, pursuant to which the Company sold securities to the Investors in a private placement transaction (the “June 2017 Offering”). Under the terms of the Purchase Agreement, the Company sold 328,300 shares of its common stock at a price of $15.23 per share, and 1,969,797 shares of its Series A Convertible Preferred Stock (the “Series A Preferred Stock”) at a price of $15.23 per share. The June 2017 Offering resulted in gross proceeds to the Company of approximately $35.0 million, and net proceeds to the Company of approximately $34.9 million. The June 2017 Offering closed on June 23, 2017. At-The-Market Issuance Sales Agreement In October 2015, the Company entered into an at-the-market issuance sales agreement (the “October 2015 Sales Agreement”), with Cowen and Company, LLC (“Cowen”), pursuant to which the Company could issue and sell shares of its common stock. In 2017 , 215,539 shares were sold for an aggregate of approximately $3.5 million in gross proceeds, and $3.4 million in net proceeds. No shares were sold in 2019 and 2018.

Cash, Cash Equivalents and Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2019

Cash and Cash Equivalents [Abstract]

Summary of cash, cash equivalents and available-for-sale marketable securities

A summary of cash, cash equivalents and

available-for-sale

marketable securities held by the Company as of December 31, 2019 and 2018 is as follows (in thousands):


	December 31, 2019
	Cost		Unrealized gains		Unrealized losses			Fair value
Cash and cash equivalents:
Cash (Level 1)	$	1,772	$	—	$	—		$	1,772
Money market funds (Level 1)		44,925		—		—			44,925
Corporate debt securities due within 3 months of date of purchase (Level 2)		—		—		—			—

Total cash and cash equivalents		46,697		—		—			46,697

Marketable securities:
Corporate debt securities due within 1 year of date of purchase (Level 2)		309,365		220		(40	)		309,545
Corporate debt securities due within 1 to 2 years of date of purchase (Level 2)		82,767		39		(3	)		82,803

Total cash, cash equivalents and marketable securities	$	438,829	$	259	$	(43	)	$	439,045


	December 31, 2018
	Cost		Unrealized gains		Unrealized losses			Fair value
Cash and cash equivalents:
Cash (Level 1)	$	2,004	$	—	$	—		$	2,004
Money market funds (Level 1)		43,401		—		—			43,401
Corporate debt securities due within 3 months of date of purchase (Level 2)		11,974		—		—			11,974

Total cash and cash equivalents		57,379		—		—			57,379

Marketable securities:
Corporate debt securities due within 1 year of date of purchase (Level 2)		426,658		14		(333	)		426,339

Total cash, cash equivalents and marketable securities	$	484,037	$	14	$	(333	)	$	483,718

Stock-based Compensation

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Stock-based Compensation

7. Stock-based Compensation

The 2015 Stock Plan, as amended, is our primary plan through which equity based grants are awarded. We ceased making new awards under the 2006 Stock Plan upon adoption of the 2015 Stock Plan. The 2015 Stock Plan provides for the grant of incentive stock options,

non-statutory

stock options, restricted stock and other stock-based compensation awards to employees, officers, directors, and consultants of the Company. The administration of the 2015 Stock Plan is under the general supervision of the Compensation Committee of the Board of Directors. The terms of stock options awarded under the 2015 Stock Plan, in general, are determined by the Compensation Committee, provided the exercise price per share generally shall not be set at less than the fair market value of a share of the common stock on the date of grant and the term shall not be greater than ten years from the date the option is granted. As of December 31, 2019, the Company had options outstanding to purchase 1,461,987 shares of its common stock, which includes options outstanding under its 2006 Stock Plan. As of December 31, 2019, 1,351,345 shares were available for future issuance.

The following table summarizes stock option activity during the twelve months ended December 31, 2019:


	Shares			Weighted average exercise price		Weighted average remaining contractual life (years)		Aggregate intrinsic value (in thousands)
Outstanding at January 1, 2019		1,132,618		$	48.52
Options granted		378,500			118.70
Options exercised		(20,131	)		11.67
Options cancelled		(29,000	)		175.78

Outstanding at December 31, 2019		1,461,987		$	64.67		7.37	$	68,604

Exercisable at December 31, 2019		943,399		$	40.38		6.94	$	63,995

The total cash received by the Company as a result of stock option exercises was $0.2 million, $2.1 million and $0.0 for the years ended December 31, 2019, 2018, and 2017. The total intrinsic value of options exercised was $2.2 million in the year ended December 31, 2019. The weighted-average grant date fair values, based on the Black-Scholes option model, of options granted during the year ended December 31, 2019, 2018 and 2017 was $91.19, $137.49 and $13.30, respectively.

Restricted Common Stock

The Company’s share-based compensation plan provides for awards of restricted shares of common stock to employees, officers, directors and consultants to the Company. Restricted stock awards are subject to forfeiture if employment or service terminates during the prescribed retention period. Restricted shares vest over the service period.

The following table summarizes restricted share activity during the year ended December 31, 2019:


	Shares			Weighted average exercise price
Outstanding at January 1, 2019		52,063		$	9.45
Vested		(52,063	)		9.45

Outstanding at December 31, 2019		—		$	—

Stock-Based Compensation Expense

Stock-based compensation expense during the years ended December 31, 2019, 2018 and 2017 was as follows (in thousands):


	Years Ended December 31,
	2019		2018		2017
Stock-based compensation expense by type of award:
Stock options	$	22,487	$	12,997	$	2,662
Restricted stock		272		492		592

Total stock-based compensation expense	$	22,759	$	13,489	$	3,254

Effect of stock-based compensation expense by line item:
Research and development	$	8,277	$	3,707	$	883
General and administrative		14,482		9,782		2,371

Total stock-based compensation expense included in net loss	$	22,759	$	13,489	$	3,254

Unrecognized stock-based compensation expense on stock options as of December 31, 2019 was $32.1 million with a weighted average remaining period of 2.7 years.

Stock-based Compensation - Stock Option (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Maximum
Stock-based compensation expense
Expiration period	10 years
Stock options
Stock-based compensation expense
Shares available for future issuance	1,351,345
Shares
Outstanding at the beginning of the year (in shares)	1,132,618
Options granted (in shares)	378,500
Options exercised (in shares)	(20,131)
Options cancelled (in shares)	(29,000)
Outstanding at the end of the year (in shares)	1,461,987	1,132,618
Exercisable at the end of the year (in shares)	943,399
Weighted average exercise price
Outstanding at the beginning of the year (in dollars per share)	$ 48.52
Options granted (in dollars per share)	118.70
Options exercised (in dollars per share)	11.67
Options cancelled (in dollars per share)	175.78
Outstanding at the end of the year (in dollars per share)	64.67	$ 48.52
Exercisable at the end of the year (in dollars per share)	$ 40.38
Weighted average remaining contractual life (years)
Outstanding at the end of the year	7 years 4 months 13 days
Exercisable at the end of the year	6 years 11 months 8 days
Aggregate intrinsic value
Outstanding at the end of the year	$ 68,604
Exercisable at the end of the year	63,995
Additional disclosures
Total intrinsic value of options exercised	2,200
Proceeds resulting from exercise of stock options	$ 200	$ 2,100	$ 0
Weighted-average grant date fair value of options (in dollars per share)	$ 91.19	$ 137.49	$ 13.30

Stockholders' Equity (Deficit) - Common Stock (Details)	12 Months Ended
Stockholders' Equity (Deficit) - Common Stock (Details)	Dec. 31, 2019 Vote
Stockholders' Equity Note [Abstract]
Number of votes per share that common stockholders are entitled to receive	1

Stock-based Compensation - Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock-based compensation expense
Stock-based compensation expense	$ 22,759	$ 13,489	$ 3,254
Research and development
Stock-based compensation expense
Stock-based compensation expense	8,277	3,707	883
General and administrative
Stock-based compensation expense
Stock-based compensation expense	14,482	9,782	2,371
Stock options
Stock-based compensation expense
Stock-based compensation expense	22,487	12,997	2,662
Unvested restricted common stock
Stock-based compensation expense
Stock-based compensation expense	$ 272	$ 492	$ 592

Cover Page - USD ($)	12 Months Ended
Cover Page - USD ($)	Dec. 31, 2019	Feb. 21, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Period End Date	Dec. 31, 2019
Document Fiscal Period Focus	FY
Entity Registrant Name	MADRIGAL PHARMACEUTICALS, INC.
Entity Central Index Key	0001157601
Entity File Number	001-33277
Current Fiscal Year End Date	--12-31
Entity Tax Identification Number	04-3508648
Entity Incorporation, State or Country Code	DE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 884,202,105
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		15,429,154
City Area Code	267
Local Phone Number	824-2827
Trading Symbol	MDGL
Security Exchange Name	NASDAQ
Title of 12(b) Security	Common Stock, $0.0001 Par Value Per Share
Entity Address, Address Line One	Four Tower Bridge
Entity Address, Address Line Two	200 Barr Harbor Drive, Suite 200
Entity Address, City or Town	West Conshohocken
Entity Address, Postal Zip Code	19428
Entity Address, State or Province	PA

Liquidity and Uncertainties (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Liquidity and Uncertainties
Net loss	$ 27,740	$ 21,429	$ 19,699	$ 15,080	$ 11,475	$ 8,512	$ 6,460	$ 6,364	$ 83,948	$ 32,811	$ 31,154
Accumulated deficit	$ 223,220				$ 139,272				$ 223,220	$ 139,272

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Summary of the outstanding securities not included in the computation of diluted net loss per common share as their inclusion would be anti-dilutive


	As of December 31,
	2019		2018		2017
Common stock options		1,461,987		1,132,618		976,777
Unvested restricted common stock		—		52,063		104,127
Preferred stock		1,969,797		1,969,797		1,969,797

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	1,969,797	1,969,797
Preferred stock, shares outstanding	1,969,797	1,969,797
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	15,429,154	15,409,023
Common stock, shares outstanding	15,429,154	15,409,023

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net loss	$ (83,948)	$ (32,811)	$ (31,154)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	22,759	13,489	3,254
Depreciation and amortization expense	112	96	77
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	332	(998)	502
Accounts payable	(1,309)	558	917
Accrued expense	16,783	(2,168)	4,087
Accrued interest, net of interest received on maturity of investments	3,647	(3,673)
Net cash used in operating activities	(41,624)	(25,507)	(22,317)
Cash flows from investing activities:
Purchases of marketable securities	(619,303)	(614,358)	(70,211)
Sales and maturities of marketable securities	650,182	234,304	48,330
Purchases of property and equipment, net of disposals	(172)	(22)	(125)
Net cash provided by (used in) investing activities	30,707	(380,076)	(22,006)
Cash flows from financing activities:
Proceeds from issuances of stock, excluding related parties, net of transaction costs		311,825	173,805
Proceeds from the sale of related party stock and exercise of common stock options, net of transaction costs	235	2,510
Net cash provided by financing activities	235	314,335	173,805
Net increase (decrease) in cash and cash equivalents	(10,682)	(91,248)	129,482
Cash and cash equivalents at beginning of period	57,379	148,627	19,145
Cash and cash equivalents at end of period	46,697	$ 57,379	148,627
Supplemental disclosure of cash flow information:
Obtaining a right-of-use asset in exchange for a lease liability	900
Purchases of property and equipment in accounts payable or accrued expenses at period end	$ 897		$ 250

Stockholders' Equity (Deficit) - At The Market Issuances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stockholders' Equity (Deficit)
Value of shares sold by the entity			$ 173,805
At-The-Market Issuance Sales Agreement
Stockholders' Equity (Deficit)
Number of shares sold by the entity	0	0	215,539
Value of shares sold by the entity			$ 3,500
Net proceeds after deducting commissions and other transactions costs			$ 3,400

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of temporary differences that give rise to deferred tax assets and liabilities

Temporary differences that give rise to deferred tax assets and liabilities are as follows (in thousands):


	For the years ended December 31,
	2019		2018		2017
Deferred Tax Liabilities
Unrealized gains on investments	$	62	$	—	$	—
Total deferred tax liabilities	$	62	$	—	$	—
Deferred Tax Assets
Charitable contributions	$	15	$	13	$	4
Accrued expenses		759		498		421
Intangibles		983		477		579
Stock compensation		10,943		4,395		605
Property, plant & equipment		13		9		—
Unrealized loss on investment		—		92		9
Net operating losses		17,635		14,851		9,229
Capitalized R&D		29,364		15,108		8,671


	For the years ended December 31,
	2019			2018			2017
R&D credit	$	6,141		$	3,505		$	1,901

Total deferred tax assets before valuation allowance		65,853			38,948			21,419
Valuation allowance		(65,791	)		(38,948	)		(21,419	)

Total deferred tax assets		62			—			—

Net deferred tax assets	$	—		$	—		$	—

Schedule of differences between the effective income tax rate and the US statutory rate

Differences between the effective income tax rate and the US statutory rate were as follows (in thousands):


	For the years ended December 31,
	2019			2018			2017
Tax benefit at U.S. federal statutory rate	$	(17,629	)	$	(6,890	)	$	(10,592	)
Stock based compensation		(47	)		(3,415	)		138
Effect of tax reform, change in federal tax rate		—			—			9,260
Other n ondeductible e xpenses		14			—			1
State income taxes benefit before valuation allowance, net of federal benefit		(6,613	)		(5,460	)		(704	)
Increase in domestic valuation allowance		26,843			17,529			2,880
Research and development credit		(2,636	)		(1,604	)		(825	)
Other adjustments		68			(160	)		(158	)

Income tax expense (benefit)	$	—		$	—		$	—

Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued Liabilities, Current [Abstract]
Contract research costs	$ 13,775	$ 571
Compensation and benefits	2,779	1,797
Professional fees	1,177	1,062
Other	5,906	2,527
Total	$ 23,637	$ 5,957

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

10. Income Taxes

At December 31, 2019, the Company had federal net operating loss (“NOL”) carryforwards of approximately $64.2 million available to reduce future taxable income,

which

$40.4 million will

expire between 203

and 2037. The Company also has state operating loss carryforwards of approximately $52.9 million, available to reduce future taxable income, which expire between 2031

nd 203

. The Company has unused federal research and development carryforwards of approximately $5.9 million which will begin to expire in 203

The Internal Revenue Code (“IRC”) limits the amounts of NOL carryforwards that a Company may use in any one year in the event of certain cumulative changes in ownership over a three-year period as described in Section 382 of the IRC. Such change in ownership could limit the Company’s utilization of the NOL, and could be triggered by subsequent sales of securities by the Company or stockholders. The deferred tax asset related to the NOL reflected on the financial statements could be affected by this limitation. Although a formal analysis has not been completed, the Company has determined that an ownership change likely occurred for Madrigal during the year ended December 31, 2017. The net operating losses are expected to be subject to an annual limitation; however, none of these NOLs is expected to expire before becoming available to reduce future taxable income.

In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. As there is no assurance of future taxable income, a full valuation allowance has been established to offset the deferred tax assets. The valuation allowance increased $26.8 million for the year ended December 31, 2019. Changes in the deferred tax asset will be recorded as an income tax benefit or expense on the accompanying consolidated statements of operations.

Entities are also required to evaluate, measure, recognize and disclose any uncertain income tax provisions taken on their income tax returns. The Company has analyzed its tax positions and has concluded that as of December 31, 2019 there were no uncertain positions. The 2013 through 2018 tax returns are open to review by the IRS and state taxing authorities. Interest and penalties, if any, as they relate to income taxes assessed, are included in the income tax provision. There was no income tax related interest and penalties included in the income tax provision for 2019.

Temporary differences that give rise to deferred tax assets and liabilities are as follows (in thousands):


	For the years ended December 31,
	2019		2018		2017
Deferred Tax Liabilities
Unrealized gains on investments	$	62	$	—	$	—
Total deferred tax liabilities	$	62	$	—	$	—
Deferred Tax Assets
Charitable contributions	$	15	$	13	$	4
Accrued expenses		759		498		421
Intangibles		983		477		579
Stock compensation		10,943		4,395		605
Property, plant & equipment		13		9		—
Unrealized loss on investment		—		92		9
Net operating losses		17,635		14,851		9,229
Capitalized R&D		29,364		15,108		8,671


	For the years ended December 31,
	2019			2018			2017
R&D credit	$	6,141		$	3,505		$	1,901

Total deferred tax assets before valuation allowance		65,853			38,948			21,419
Valuation allowance		(65,791	)		(38,948	)		(21,419	)

Total deferred tax assets		62			—			—

Net deferred tax assets	$	—		$	—		$	—

Differences between the effective income tax rate and the US statutory rate were as follows (in thousands):


	For the years ended December 31,
	2019			2018			2017
Tax benefit at U.S. federal statutory rate	$	(17,629	)	$	(6,890	)	$	(10,592	)
Stock based compensation		(47	)		(3,415	)		138
Effect of tax reform, change in federal tax rate		—			—			9,260
Other n ondeductible e xpenses		14			—			1
State income taxes benefit before valuation allowance, net of federal benefit		(6,613	)		(5,460	)		(704	)
Increase in domestic valuation allowance		26,843			17,529			2,880
Research and development credit		(2,636	)		(1,604	)		(825	)
Other adjustments		68			(160	)		(158	)

Income tax expense (benefit)	$	—		$	—		$	—

Quarterly Financial Data (unaudited) (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Schedule of quarterly results of operations

The following tables present a summary of quarterly results of operations for 2019 and 2018 (in thousands, except shares and per share data):


	Three months ended
	March 31, 2019			June 30, 2019			September 30, 2019			December 31, 2019
	March 31, 2019			June 30, 2019			September 30, 2019			December 31, 2019
Revenues:
Total revenues	$	—		$	—		$	—		$	—
Operating expenses:
Research and development		12,373			15,594			19,447			24,910
General and administrative		5,746			7,110			4,748			5,044

Total operating expenses		18,119			22,704			24,195			29,954

Loss from operations		(18,119	)		(22,704	)		(24,195	)		(29,954	)
Interest income		3,039			3,005			2,766			2,214
Other income		—			—			—			—

Net loss	$	(15,080	)	$	(19,699	)	$	(21,429	)	$	(27,740	)

Net loss per common share:
Basic and diluted net loss per common share	$	(0.98	)	$	(1.28	)	$	(1.39	)	$	(1.80	)
Basic and diluted weighted average number of common shares outstanding		15,364,465			15,368,986			15,415,096			15,429,154


	Three months ended
	March 31, 2018			June 30, 2018			September 30, 2018			December 31, 2018
	March 31, 2018			June 30, 2018			September 30, 2018			December 31, 2018
Revenues:
Total revenues	$	—		$	—		$	—		$	—
Operating expenses:
Research and development		5,198			5,109			6,211			8,871
General and administrative		1,871			2,717			5,122			5,583

Total operating expenses		7,069			7,826			11,333			14,454

Loss from operations		(7,069	)		(7,826	)		(11,333	)		(14,454	)
Interest income		705			1,166			2,821			2,979
Other income		—			200			—			—

Net loss	$	(6,364	)	$	(6,460	)	$	(8,512	)	$	(11,475	)

Net loss per common share:
Basic and diluted net loss per common share	$	(0.45	)	$	(0.45	)	$	(0.56	)	$	(0.75	)
Basic and diluted weighted average number of common shares outstanding		14,127,868			14,383,720			15,307,872			15,348,358

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies The Company has a Research, Development and Commercialization Agreement with Hoffmann-La Roche (“Roche”) which grants the Company a sole and exclusive license to develop, use, sell, offer for sale and import any Licensed Product as defined by the agreement. The agreement requires future milestone payments to Roche. In 2019, the Company commenced a Phase 3 study in Non-Alcoholic Steatohepatitis (NASH), which triggered a $2 million milestone payment under the agreement. Remaining milestones under the agreement total $8 million and are earned by achieving specified objectives related to future regulatory approval in the United States and Europe of a product developed from resmetirom. A single-digit royalty payment range is based on net sales of products developed from resmetirom, subject to certain reductions. Except as described above, the Company has not achieved any additional product development or regulatory milestones and had no Licensed Product sales for the years ended December 31, 2019, 2018 and 2017. The Company has entered into customary contractual arrangements and letters of intent in preparation for and in support of the Phase 3 clinical trials.

Accrued Liabilities (Tables)

12 Months Ended

Dec. 31, 2019

Accrued Liabilities, Current [Abstract]

Schedule of Accrued Liabilities

Accrued liabilities as of December 31, 2019 and 2018 consisted of the following (in thousands):


	December 31, 2019		December 31, 2018
C ontract research costs	$	13,775	$	571
Compensation and benefits		2,779		1,797
Professional fees		1,177		1,062
Other		5,906		2,527

	$	23,637	$	5,957

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating expenses:
Research and development	$ 72,324	$ 25,389	$ 24,390
General and administrative	22,648	15,293	7,672
Total operating expenses	94,972	40,682	32,062
Loss from operations	(94,972)	(40,682)	(32,062)
Interest income	11,024	7,671	558
Other income		200	350
Net loss	$ (83,948)	$ (32,811)	$ (31,154)
Net loss per common share:
Basic and diluted net loss per common share (in dollars per share)	$ (5.45)	$ (2.22)	$ (2.54)
Basic and diluted weighted average number of common shares outstanding	15,394,659	14,796,712	12,244,939

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Principle of Consolidation

The consolidated financial statements include the financial statements of the Company and its wholly owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect certain reported amounts of assets and liabilities, and the reported amounts of revenues and expenses during the reporting periods. The Company bases its estimates on historical experience and various other assumptions that management believes to be reasonable under the circumstances. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.

Cash and Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents. The Company maintains its cash in bank accounts, the balance of which, at times, exceeds Federal Deposit Insurance Corporation insured limits.

The primary objective of the Company’s investment activities is to preserve its capital for the purpose of funding operations and the Company does not enter into investments for trading or speculative purposes. The Company’s cash is deposited in highly rated financial institutions in the United States. The Company invests in money market funds and high-grade, commercial paper and corporate bonds, which management believes are subject to minimal credit and market risk.

Marketable Securities

Marketable securities consist of investments in high-grade corporate obligations, and government and government agency obligations that are classified as

available-for-sale.

Since these securities are available to fund current operations they are classified as current assets on the consolidated balance sheets.

The Company adjusts the cost of

available-for-sale

debt securities for amortization of premiums and accretion of discounts to maturity. The Company includes such amortization and accretion as a component of interest income, net. Realized gains and losses and declines in value, if any, that the Company judges to be other-than-temporary on

available-for-sale

securities are reported as a component of interest income. To determine whether an other-than-temporary impairment exists, the Company considers whether it intends to sell the debt security and, if the Company does not intend to sell the debt security, it considers available evidence to assess whether it is more likely than not that it will be required to sell the security before the recovery of its amortized cost basis. During the years ended December 31, 2019, 2018 and 2017, the Company determined it did not have any securities that were other-than-temporarily impaired.

Marketable securities are stated at fair value, including accrued interest, with their unrealized gains and losses included as a component of accumulated other comprehensive income or loss, which is a separate component of stockholders’ equity. The fair value of these securities is based on quoted prices and observable inputs on a recurring basis. Realized gains and losses are determined on the specific identification method. During the years ended December 31, 2019, 2018 and 2017, the Company did not have any realized gains or losses on marketable securities.

Fair Value of Financial Instruments

The carrying amounts of the Company’s financial instruments, which include cash equivalents, and marketable securities, approximate their fair values. The fair value of the Company’s financial instruments reflects the amounts that would be received upon sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The fair value hierarchy has the following three levels:

Level 1—quoted prices in active markets for identical assets and liabilities.

Level 2—observable inputs other than Level 1 inputs. Examples of Level 2 inputs include quoted prices in active markets for similar assets or liabilities and quoted prices for identical assets or liabilities in markets that are not active.

Level 3—unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability.

Financial assets and liabilities are classified in their entirety within the fair value hierarchy based on the lowest level of input that is significant to the fair value measurement. The Company measures the fair value of its marketable securities by taking into consideration valuations obtained from third-party pricing sources. The pricing services utilize industry standard valuation models, including both income and market based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker-dealer quotes on the same or similar securities, issuer credit spreads, benchmark securities and other observable inputs.

As of December 31, 2019 and 2018, the Company’s financial assets valued based on Level 1 inputs consisted of cash and cash equivalents in a money market fund and its financial assets valued based on Level 2 inputs consisted of high-grade corporate bonds and commercial paper. During the years ended December 31, 2019, 2018 and 2017, the Company did not have any transfers of financials assets between Levels 1 and 2. As of December 31, 2019 and 2018, the Company did not have any financial liabilities that were recorded at fair value on a recurring basis on the balance sheet.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development costs are comprised of costs incurred in performing research and development activities, including internal costs (including

tock

based compensation), costs for consultants, milestone payments under licensing agreements, and other costs associated with the Company’s preclinical and clinical programs. In particular, the Company has conducted safety studies in animals, optimized and implemented the manufacturing of our drug, and conducted Phase

1-3

clinical trials, all of which are considered research and development expenditures. Management uses significant judgment in estimating the amount of research and development costs recognized in each reporting period. Management analyzes and estimates the progress of its preclinical studies and clinical trials, completion of milestones events per underlying agreements, invoices received and contracted costs when estimating the research and development costs to accrue in each reporting period. Actual results could differ from the Company’s estimates. The Company’s historical estimates for research and development costs have not been materially different from the actual costs.

Patents

Costs to secure and defend patents are expensed as incurred and are classified as general and administrative expense in the Company’s statements of operations. Patent expenses were approximately $408 thousand, $226 thousand and $176 thousand for the years ended December 31, 2019, 2018 and 2017, respectively.

Stock-Based Compensation

The Company recognizes stock-based compensation expense based on the grant date fair value of stock options granted to employees, officers and directors. The Company uses the Black-Scholes option pricing model to determine the grant date fair value as management believes it is the most appropriate valuation method for its option grants. The Black-Scholes model requires inputs for risk-free interest rate, dividend yield, volatility and expected lives of the options. The expected lives for options granted represent the period of time that options granted are expected to be outstanding. The Company uses the simplified method for determining the expected lives of options. Expected volatility is based upon an industry estimate or blended rate including the Company’s historical trading activity. The risk-free rate for periods within the expected life of the option is based on the U.S. Treasury yield curve in effect at the time of the grant. The Company estimates the forfeiture rate based on historical data. This analysis is

re-evaluated

at least annually and the forfeiture rate is adjusted as necessary.

Certain of the employee stock options granted by the Company are structured to qualify as incentive stock options (ISOs). Under current tax regulations, the Company does not receive a tax deduction for the issuance, exercise or disposition of ISOs if the employee meets certain holding requirements. If the employee does not meet the holding requirements, a disqualifying disposition occurs, at which time the Company may receive a tax deduction. The Company does not record tax benefits related to ISOs unless and until a disqualifying disposition is reported. In the event of a disqualifying disposition, the entire tax benefit is recorded as a reduction of income tax expense. The Company has not recognized any income tax benefit for its share-based compensation arrangements due to the fact that the Company does not believe it is more likely than not it will realize the related deferred tax assets.

Income Taxes

The Company uses the asset and liability method to account for income taxes. Deferred tax assets and liabilities are determined based on the expected future tax consequences of temporary differences between the Company’s financial statement carrying amounts and the tax basis of assets and liabilities using enacted tax rates expected to be in effect in the years in which the differences are expected to reverse. The Company currently maintains a 100% valuation allowance on its deferred tax assets.

Comprehensive Loss

Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from

non-owner

sources. Changes in unrealized gains and losses on marketable securities represent the only difference between the Company’s net loss and comprehensive loss.

Basic and Diluted Loss Per Common Share

Basic net loss per share is computed using the weighted average number of common shares outstanding during the period, excluding restricted stock that has been issued but is not yet vested. Diluted net loss per common share is computed using the weighted average number of common shares outstanding and the weighted average dilutive potential common shares outstanding using the treasury stock method. However, for the years ended December 31, 2019, 2018 and 2017, diluted net loss per share is the same as basic net loss per share as the inclusion of weighted average shares of unvested restricted common stock and common stock issuable upon the exercise of stock options would be anti-dilutive.

The following table summarizes outstanding securities not included in the computation of diluted net loss per common share as their inclusion would be anti-dilutive:


	As of December 31,
	2019		2018		2017
Common stock options		1,461,987		1,132,618		976,777
Unvested restricted common stock		—		52,063		104,127
Preferred stock		1,969,797		1,969,797		1,969,797

Recent Accounting Pronouncements

In February 2016, the FASB issued ASU

2016-02,

“Leases,” which, together with amendments comprising ASC 842, requires lessees to identify arrangements that should be accounted for as leases and generally recognized, for operating and finance leases with terms exceeding twelve months, a

right-of-use

asset (or “ROU”) and lease liability on the balance sheet. For public business entities, ASU

2016-02

is effective for annual and interim reporting periods beginning after December 15, 2018, with early adoption permitted. A modified retrospective transition approach is required, applying the new standard to all leases existing at the date of initial application. The Company adopted ASU

2016-02

effective January 1, 2019.

Based on the modified retrospective transition approach, there

was no significant retrospective impact from the adoption. The new standard provides a number of optional practical expedients in transition. We have elected the package of practical expedients, which permits us not to reassess under the new standard our prior conclusions about lease identification, lease classification and initial direct costs. The new standard also provides practical expedients for an entity’s ongoing accounting. We have elected the short-term lease exception and we will not recognize ROU assets or lease liabilities for qualifying leases (leases with a term of less than 12 months from lease commencement). In 2019, the Company accounted for a new lease under the guidance (see Note 8).

Summary of Significant Accounting Policies - Income Taxes (Details)	12 Months Ended
	Dec. 31, 2019
Income Taxes
Valuation allowance on deferred tax assets (as a percent)	100.00%

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Principle of Consolidation

Use of Estimates

Cash and Cash Equivalents

Marketable Securities

Marketable securities consist of investments in high-grade corporate obligations, and government and government agency obligations that are classified as

available-for-sale.

Since these securities are available to fund current operations they are classified as current assets on the consolidated balance sheets.

The Company adjusts the cost of

available-for-sale

Fair Value of Financial Instruments

Level 1—quoted prices in active markets for identical assets and liabilities.

Level 3—unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability.

Research and Development Costs

tock

1-3

Patents

Stock-Based Compensation

re-evaluated

at least annually and the forfeiture rate is adjusted as necessary.

Income Taxes

Comprehensive Loss

Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from

non-owner

sources. Changes in unrealized gains and losses on marketable securities represent the only difference between the Company’s net loss and comprehensive loss.

Basic and Diluted Loss Per Common Share

The following table summarizes outstanding securities not included in the computation of diluted net loss per common share as their inclusion would be anti-dilutive:


	As of December 31,
	2019		2018		2017
Common stock options		1,461,987		1,132,618		976,777
Unvested restricted common stock		—		52,063		104,127
Preferred stock		1,969,797		1,969,797		1,969,797

Recent Accounting Pronouncements

In February 2016, the FASB issued ASU

2016-02,

right-of-use

asset (or “ROU”) and lease liability on the balance sheet. For public business entities, ASU

2016-02

effective January 1, 2019.

Based on the modified retrospective transition approach, there

Cash, Cash Equivalents and Marketable Securities

12 Months Ended

Dec. 31, 2019

Cash and Cash Equivalents [Abstract]

Cash, Cash Equivalents and Marketable Securities

4. Cash, Cash Equivalents and Marketable Securities

A summary of cash, cash equivalents and

available-for-sale

marketable securities held by the Company as of December 31, 2019 and 2018 is as follows (in thousands):


	December 31, 2019
	Cost		Unrealized gains		Unrealized losses			Fair value
Cash and cash equivalents:
Cash (Level 1)	$	1,772	$	—	$	—		$	1,772
Money market funds (Level 1)		44,925		—		—			44,925
Corporate debt securities due within 3 months of date of purchase (Level 2)		—		—		—			—

Total cash and cash equivalents		46,697		—		—			46,697

Marketable securities:
Corporate debt securities due within 1 year of date of purchase (Level 2)		309,365		220		(40	)		309,545
Corporate debt securities due within 1 to 2 years of date of purchase (Level 2)		82,767		39		(3	)		82,803

Total cash, cash equivalents and marketable securities	$	438,829	$	259	$	(43	)	$	439,045


	December 31, 2018
	Cost		Unrealized gains		Unrealized losses			Fair value
Cash and cash equivalents:
Cash (Level 1)	$	2,004	$	—	$	—		$	2,004
Money market funds (Level 1)		43,401		—		—			43,401
Corporate debt securities due within 3 months of date of purchase (Level 2)		11,974		—		—			11,974

Total cash and cash equivalents		57,379		—		—			57,379

Marketable securities:
Corporate debt securities due within 1 year of date of purchase (Level 2)		426,658		14		(333	)		426,339

Total cash, cash equivalents and marketable securities	$	484,037	$	14	$	(333	)	$	483,718

Income Taxes - Net Operating Loss Carryforwards (Details) $ in Millions	Dec. 31, 2019 USD ($)
Federal
Income Taxes
Net operating loss	$ 64.2
Federal \| Expire In 2037 [Member]
Income Taxes
Net operating loss	40.4
State
Income Taxes
Net operating loss	$ 52.9

Summary of Significant Accounting Policies - Basic and Diluted Loss Per Common Share (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock options
Anti-dilutive securities
Outstanding securities not included in the computation of diluted net loss per common share as their inclusion would be anti-dilutive (in shares)	1,461,987	1,132,618	976,777
Unvested restricted common stock
Anti-dilutive securities
Outstanding securities not included in the computation of diluted net loss per common share as their inclusion would be anti-dilutive (in shares)		52,063	104,127
Preferred Stock
Anti-dilutive securities
Outstanding securities not included in the computation of diluted net loss per common share as their inclusion would be anti-dilutive (in shares)	1,969,797	1,969,797	1,969,797

Summary of Significant Accounting Policies - Patents (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Patent expenses	$ 408	$ 226	$ 176

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common stock	Additional paid-in Capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Balance at Dec. 31, 2016	$ 36,410		$ 1	$ 111,691	$ 25	$ (75,307)
Balance (in shares) at Dec. 31, 2016			11,951,866
Increase (Decrease) in Stockholders' Equity
Issuance of common and preferred shares in equity offerings, net of transaction costs	173,805			173,805
Issuance of common and preferred shares in equity offerings, net of transaction costs (in shares)		1,969,797	2,275,768
Compensation expense related to stock options for services	3,254			3,254
Unrealized gain (loss) on marketable securities	(56)				(56)
Net loss	(31,154)					(31,154)
Balance at Dec. 31, 2017	182,259		$ 1	288,750	(31)	(106,461)
Balance (in shares) at Dec. 31, 2017		1,969,797	14,227,634
Increase (Decrease) in Stockholders' Equity
Issuance of common shares in equity offering, excluding to related parties, net of transaction costs	311,825		$ 1	311,824
Issuance of common shares in equity offering, excluding to related parties, net of transaction costs (in shares)			1,079,580
Sale of common shares to related parties and exercise of common stock options, net of transaction cost	2,510			2,510
Sale of common shares to related parties and exercise of common stock options, net of transaction cost ( in shares)			101,809
Compensation expense related to stock options for services	13,489			13,489
Unrealized gain (loss) on marketable securities	(288)				(288)
Net loss	(32,811)					(32,811)
Balance at Dec. 31, 2018	$ 476,984		$ 2	616,573	(319)	(139,272)
Balance (in shares) at Dec. 31, 2018	15,409,023	1,969,797	15,409,023
Increase (Decrease) in Stockholders' Equity
Sale of common shares to related parties and exercise of common stock options, net of transaction cost	$ 235			235
Sale of common shares to related parties and exercise of common stock options, net of transaction cost ( in shares)			20,131
Compensation expense related to stock options for services	22,759			22,759
Unrealized gain (loss) on marketable securities	535				535
Net loss	(83,948)					(83,948)
Balance at Dec. 31, 2019	$ 416,565		$ 2	$ 639,567	$ 216	$ (223,220)
Balance (in shares) at Dec. 31, 2019	15,429,154	1,969,797	15,429,154

Stock-based Compensation - Restricted Common Stock (Details) - Unvested restricted common stock	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Shares
Outstanding at January 1, 2019 \| shares	52,063
Vested (in shares) \| shares	(52,063)
Outstanding at December 31, 2018 \| shares	0
Weighted average grant date fair value
Outstanding at January 1, 2019 (in dollars per share) \| $ / shares	$ 9.45
Vested (in dollars per share) \| $ / shares	9.45
Outstanding at December 31, 2019 (in dollars per share) \| $ / shares	$ 0

Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash, Cash Equivalents and Marketable Securities
Total cash, cash equivalents and marketable securities, Unrealized gains	$ 259	$ 14
Total cash, cash equivalents and marketable securities, Unrealized losses	(43)	(333)
Carrying value
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	46,697	57,379
Total cash, cash equivalents and marketable securities, Cost	438,829	484,037
Fair value
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	46,697	57,379
Total cash, cash equivalents and marketable securities, Fair value	$ 439,045	$ 483,718
Corporate debt securities due within 3 months of date of purchase
Cash, Cash Equivalents and Marketable Securities
Maturity period from date of purchase to classify an investment as marketable securities	3 months	3 months
Corporate debt securities due within 3 months of date of purchase \| Carrying value \| Level 2
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents		$ 11,974
Corporate debt securities due within 3 months of date of purchase \| Fair value \| Level 2
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents		$ 11,974
Corporate debt securities due within 1 year of date of purchase
Cash, Cash Equivalents and Marketable Securities
Maturity period from date of purchase to classify an investment as marketable securities	1 year	1 year
Corporate debt securities due within 1 year of date of purchase \| Level 2
Cash, Cash Equivalents and Marketable Securities
Marketable securities, unrealized gains	$ 220	$ 14
Marketable securities, unrealized losses	(40)	(333)
Corporate debt securities due within 1 year of date of purchase \| Carrying value \| Level 2
Cash, Cash Equivalents and Marketable Securities
Marketable securities, cost	309,365	426,658
Corporate debt securities due within 1 year of date of purchase \| Fair value \| Level 2
Cash, Cash Equivalents and Marketable Securities
Marketable securities, fair value	$ 309,545	426,339
Corporate debt securities due within 1 to 2 years of date of purchase \| Maximum [Member]
Cash, Cash Equivalents and Marketable Securities
Maturity period from date of purchase to classify an investment as marketable securities	2 years
Corporate debt securities due within 1 to 2 years of date of purchase \| Minimum [Member]
Cash, Cash Equivalents and Marketable Securities
Maturity period from date of purchase to classify an investment as marketable securities	1 year
Corporate debt securities due within 1 to 2 years of date of purchase \| Level 2
Cash, Cash Equivalents and Marketable Securities
Marketable securities, unrealized gains	$ 39
Marketable securities, unrealized losses	(3)
Corporate debt securities due within 1 to 2 years of date of purchase \| Carrying value \| Level 2
Cash, Cash Equivalents and Marketable Securities
Marketable securities, cost	82,767
Corporate debt securities due within 1 to 2 years of date of purchase \| Fair value \| Level 2
Cash, Cash Equivalents and Marketable Securities
Marketable securities, fair value	82,803
Cash \| Carrying value \| Level 1
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	1,772	2,004
Cash \| Fair value \| Level 1
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	1,772	2,004
Money market funds \| Carrying value \| Level 1
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	44,925	43,401
Money market funds \| Fair value \| Level 1
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	$ 44,925	$ 43,401

Stock-based Compensation - Unrecognized Expense (Details) - Stock options $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Unrecognized stock-based compensation expense
Unrecognized stock compensation expense	$ 32.1
Weighted average remaining period (in years)	2 years 8 months 12 days

Stockholders' Equity (Deficit) - Registered Offering (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Dec. 31, 2017
Stockholders' Equity (Deficit)
Value of shares sold by the entity			$ 173,805
Registered Offering \| Common stock \| Goldman Sachs & Co. LLC \| Underwriting Agreement
Stockholders' Equity (Deficit)
Number of shares sold by the entity	1,079,580	1,731,929
Number of days granted to purchase additional shares	30 days	30 days
Issue price of stock	$ 305.00	$ 83.00	$ 83.00
Value of shares sold by the entity	$ 329,300	$ 143,800
Net proceeds after deducting commissions and other transactions costs	$ 311,800	$ 135,700
Additional Shares \| Common stock \| Goldman Sachs & Co. LLC \| Underwriting Agreement
Stockholders' Equity (Deficit)
Number of shares sold by the entity	95,973	225,904

Quarterly Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating expenses:
Research and development	$ 24,910	$ 19,447	$ 15,594	$ 12,373	$ 8,871	$ 6,211	$ 5,109	$ 5,198	$ 72,324	$ 25,389	$ 24,390
General and administrative	5,044	4,748	7,110	5,746	5,583	5,122	2,717	1,871	22,648	15,293	7,672
Total operating expenses	29,954	24,195	22,704	18,119	14,454	11,333	7,826	7,069	94,972	40,682	32,062
Loss from operations	(29,954)	(24,195)	(22,704)	(18,119)	(14,454)	(11,333)	(7,826)	(7,069)	(94,972)	(40,682)	(32,062)
Interest income	2,214	2,766	3,005	3,039	2,979	2,821	1,166	705
Other income							200			200	350
Net loss	$ (27,740)	$ (21,429)	$ (19,699)	$ (15,080)	$ (11,475)	$ (8,512)	$ (6,460)	$ (6,364)	$ (83,948)	$ (32,811)	$ (31,154)
Basic and diluted net loss per common share (in dollars per share)	$ (1.80)	$ (1.39)	$ (1.28)	$ (0.98)	$ (0.75)	$ (0.56)	$ (0.45)	$ (0.45)	$ (5.45)	$ (2.22)	$ (2.54)
Basic and diluted weighted average number of common shares outstanding	15,429,154	15,415,096	15,368,986	15,364,465	15,348,358	15,307,872	14,383,720	14,127,868	15,394,659	14,796,712	12,244,939

Liquidity and Uncertainties	12 Months Ended
Liquidity and Uncertainties	Dec. 31, 2019
Liquidity and Uncertainties
Liquidity and Uncertainties	3. Liquidity and Uncertainties The Company is subject to risks common to development stage companies in the Bio-Pharmaceutical industry including, but not limited to, uncertainty of product development and commercialization, dependence on key personnel, uncertainty of market acceptance of products and product reimbursement, product liability, uncertain protection of proprietary technology, potential inability to raise additional financing necessary for development and commercialization, and compliance with the U.S. Food and Drug Administration and other government regulations. The Company has incurred losses since inception, including approximately $83.9 million for the year ended December 31, 2019, resulting in an accumulated deficit of approximately $223.2 million and $139.3 million as of December 31, 2019 and 2018, respectively. Management expects to incur losses for the foreseeable future. To date, the Company has funded its operations primarily through the issuance of convertible debt, the proceeds from the Merger on July 22, 2016, and proceeds from sales of the Company’s common and Series A Convertible Preferred Stock (see Note 6). The Company believes that its cash, cash equivalents and marketable securities at December 31, 2019 will be sufficient to fund operations past one year from the issuance of these financial statements. To meet its future capital needs, the Company intends to raise additional capital through debt or equity financings, collaborations, partnerships or other strategic transactions. However, there can be no assurance that the Company will be able to complete any such transactions on acceptable terms or otherwise. The inability of the Company to obtain sufficient funds on acceptable terms when needed could have a material adverse effect on the Company’s business, results of operations and financial condition. The Company has the ability to delay certain research activities and related clinical expenses if necessary due to liquidity concerns until a date in which those concerns are relieved.

Stockholders' Equity (Deficit) - June 2017 Private Placement (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Stockholders' Equity (Deficit)
Value of shares sold by the entity			$ 173,805
Net proceeds after deducting commissions and other transactions costs		$ 311,825	$ 173,805
Private Placement Offering \| Purchase Agreement
Stockholders' Equity (Deficit)
Value of shares sold by the entity	$ 35,000
Net proceeds after deducting commissions and other transactions costs	$ 34,900
Private Placement Offering \| Common stock \| Purchase Agreement
Stockholders' Equity (Deficit)
Number of shares sold by the entity	328,300
Issue price of stock	$ 15.23
Private Placement Offering \| Series A Convertible Preferred Stock \| Purchase Agreement
Stockholders' Equity (Deficit)
Number of shares sold by the entity	1,969,797
Issue price of stock	$ 15.23

Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details)	12 Months Ended
	Dec. 31, 2019
Recent Accounting Pronouncements
Lease, Practical Expedients, Package [true false]	true

Accrued Liabilities

12 Months Ended

Dec. 31, 2019

Accrued Liabilities, Current [Abstract]

Accrued Liabilities

5. Accrued Liabilities

Accrued liabilities as of December 31, 2019 and 2018 consisted of the following (in thousands):


	December 31, 2019		December 31, 2018
C ontract research costs	$	13,775	$	571
Compensation and benefits		2,779		1,797
Professional fees		1,177		1,062
Other		5,906		2,527

	$	23,637	$	5,957

Leases (Details) - USD ($) $ in Thousands	12 Months Ended
Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2021	$ 363
2022	371
2022	31
Total minimum payments	765
Less: imputed interest	89
Present value of lease liabilities	$ 676
Weighted average, operating lease term	2 years
Weighted average, operating discount rate	5.50%
Lease Liability paid in cash	$ 297
Operating lease costs	$ 386
Operating Leases Rent Expense		$ 239	$ 134