Organization	12 Months Ended
Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	1. Organization MyoKardia, Inc. (the Company) is a clinical-stage biopharmaceutical company pioneering a precision medicine approach to discover, develop and commercialize targeted therapies for the treatment of serious and neglected rare cardiovascular diseases. The Company’s initial focus is on the treatment of cardiomyopathies, a group of diseases of the heart muscle. MyoKardia’s pipeline includes mavacamten and MYK-224, which are being studied for the treatment of hypertrophic cardiomyopathy, LUS-1, being studied for the treatment of diseases of diastolic dysfunction and danicamtiv (formerly MYK-491) and ACT-1, being studied for the treatment of diseases of systolic dysfunction. MyoKardia’s most advanced programs are: mavacamten, which is in four clinical trials including a Phase 3 study in patients with hypertrophic cardiomyopathy (HCM); danicamtiv, which recently completed a Phase 2a multiple-ascending dose study in patients with stable systolic heart failure and is being advanced to a Phase 2 study in patients with genetic dilated cardiomyopathy; and MYK-224, which is in a Phase 1 randomized, placebo-controlled study in healthy volunteers. The Company was incorporated on June 8, 2012 in Delaware. As of December 31, 2019, its corporate headquarters and operations were located in South San Francisco, California and as of the date of this filing its corporate headquarters and operations are located in Brisbane, California. Liquidity The Company has incurred significant operating losses since inception and has an accumulated deficit of $478.8 million as of December 31, 2019. The Company has relied on its ability to fund its operations through private and public equity financings and to a lesser extent, through a license and collaboration arrangement with a collaboration partner, Sanofi S.A. (Sanofi) via its subsidiary, Aventis, Inc. As discussed further in Note 3, the collaboration agreement ended on December 31, 2018 and the Company had no revenues relating to its Sanofi collaboration in 2019, nor has it received reimbursements of research and development expenses after June 30, 2019. The Company has not yet received regulatory approval to commercialize or sell any product and does not have customers. Management expects operating losses and negative operating cash flows to continue for the foreseeable future. As the Company continues to incur losses, a transition to profitability is dependent upon the successful development, approval, and commercialization of the Company’s products and product candidates and the achievement of a level of revenues adequate to support its cost structure. The Company’s ultimate success depends on the outcome of its research and development activities and anticipates the need to raise additional capital to fully implement its business plan. The Company intends to raise such capital through the issuance of additional equity, debt and/or strategic alliances with partner companies. There is no assurance that such financing will be available or that such strategic alliances will be executed, on terms acceptable to the Company, or at all. As of December 31, 2019, the Company had $430.3 million of cash, cash equivalents and short and long-term investments, which management believes will be sufficient to meet the Company’s anticipated operating and capital expenditure requirements for the twelve months following the date of issuance of these financial statements. Management’s belief with respect to its ability to fund operations is based on estimates that are subject to risks and uncertainties. If actual results are different from management’s estimates, the Company may need to seek additional funding.

Organization

12 Months Ended

Dec. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

1. Organization

MyoKardia, Inc. (the Company) is a clinical-stage biopharmaceutical company pioneering a precision medicine approach to discover, develop and commercialize targeted therapies for the treatment of serious and neglected rare cardiovascular diseases. The Company’s initial focus is on the treatment of cardiomyopathies, a group of diseases of the heart muscle. MyoKardia’s pipeline includes mavacamten and MYK-224, which are being studied for the treatment of hypertrophic cardiomyopathy, LUS-1, being studied for the treatment of diseases of diastolic dysfunction and danicamtiv (formerly MYK-491) and ACT-1, being studied for the treatment of diseases of systolic dysfunction.

MyoKardia’s most advanced programs are: mavacamten, which is in four clinical trials including a Phase 3 study in patients with hypertrophic cardiomyopathy (HCM); danicamtiv, which recently completed a Phase 2a multiple-ascending dose study in patients with stable systolic heart failure and is being advanced to a Phase 2 study in patients with genetic dilated cardiomyopathy; and MYK-224, which is in a Phase 1 randomized, placebo-controlled study in healthy volunteers.

The Company was incorporated on June 8, 2012 in Delaware. As of December 31, 2019, its corporate headquarters and operations were located in South San Francisco, California and as of the date of this filing its corporate headquarters and operations are located in Brisbane, California.

Liquidity

The Company has incurred significant operating losses since inception and has an accumulated deficit of $478.8 million as of December 31, 2019. The Company has relied on its ability to fund its operations through private and public equity financings and to a lesser extent, through a license and collaboration arrangement with a collaboration partner, Sanofi S.A. (Sanofi) via its subsidiary, Aventis, Inc. As discussed further in Note 3, the collaboration agreement ended on December 31, 2018 and the Company had no revenues relating to its Sanofi collaboration in 2019, nor has it received reimbursements of research and development expenses after June 30, 2019. The Company has not yet received regulatory approval to commercialize or sell any product and does not have customers. Management expects operating losses and negative operating cash flows to continue for the foreseeable future. As the Company continues to incur losses, a transition to profitability is dependent upon the successful development, approval, and commercialization of the Company’s products and product candidates and the achievement of a level of revenues adequate to support its cost structure. The Company’s ultimate success depends on the outcome of its research and development activities and anticipates the need to raise additional capital to fully implement its business plan. The Company intends to raise such capital through the issuance of additional equity, debt and/or strategic alliances with partner companies. There is no assurance that such financing will be available or that such strategic alliances will be executed, on terms acceptable to the Company, or at all.

As of December 31, 2019, the Company had $430.3 million of cash, cash equivalents and short and long-term investments, which management believes will be sufficient to meet the Company’s anticipated operating and capital expenditure requirements for the twelve months following the date of issuance of these financial statements. Management’s belief with respect to its ability to fund operations is based on estimates that are subject to risks and uncertainties. If actual results are different from management’s estimates, the Company may need to seek additional funding.