Formation and Business of the Company	9 Months Ended
Sep. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Formation and Business of the Company	1. Formation and Business of the Company 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. Our initial focus is on the treatment of heritable cardiomyopathies, a group of rare, genetically-driven forms of heart failure that result from biomechanical defects in cardiac muscle contraction. We have used our precision medicine platform to generate a robust pipeline of therapeutic programs for the chronic treatment of the two most common forms of heritable cardiomyopathy—hypertrophic cardiomyopathy (“HCM”), and dilated cardiomyopathy (“DCM”). The Company has completed enrollment in a Phase 2 clinical trial of mavacamten (formerly known as MYK-461), our product candidate for the treatment of HCM, and is currently enrolling subjects in a Phase 1 clinical trial of MYK-491, our product candidate for the treatment of DCM. Using our precision medicine development strategy, we believe we have efficiently generated clinical proof of mechanism for mavacamten in both healthy volunteers and in HCM patients, and we intend to pursue a similar path for MYK-491. In 2016, mavacamten was granted Orphan Drug Designation by the U.S. Food and Drug Administration (“FDA”), for the treatment of symptomatic, obstructive hypertrophic cardiomyopathy (“oHCM”), a subset of HCM. Through September 30, 2017, the Company has financed its operations through an initial public offering (“IPO”), two follow-on public offerings, private placements of redeemable convertible preferred stock and funds received in connection with a license and collaboration agreement with Aventis Inc., a wholly-owned subsidiary of Sanofi S.A., entered into in August 2014 (the “Collaboration Agreement”) (See Note 4). The Company received net proceeds of $93.9 million from the sale of shares of its Series A, A-1 and B redeemable convertible preferred stock. On November 3, 2015, the Company completed its IPO of 6,253,125 shares of common stock at an offering price of $10.00 per share, resulting in net proceeds of approximately $55.6 million, after deducting underwriting discounts, commissions and offering costs. On October 3, 2016, the Company completed a follow-on public offering of 4,370,000 shares of common stock at an offering price of $15.00 per share, resulting in net proceeds of approximately $61.1 million, after deducting underwriting discounts, commissions and estimated offering costs. On August 14, 2017, the Company completed another follow-on public offering of 4,025,000 shares of common stock at an offering price of $35.50 per share, resulting in net proceeds of approximately $133.8 million, after deducting underwriting discounts, commissions and estimated offering costs. In connection with the Collaboration Agreement, the Company has received $105.0 million from Sanofi S.A., consisting of a $35.0 million upfront payment, a $25.0 million milestone payment for the submission of an investigational new drug application (“IND”) for MYK-491 with the FDA in November 2016, and a $45.0 million continuation payment from Sanofi in January 2017. As of September 30, 2017, the Company had an accumulated deficit of $116.4 million and cash and cash equivalents of $227.2 million, short-term investments of $20.0 million and long-term investments of $36.0 million. The accompanying unaudited Condensed Consolidated Financial Statements, in the opinion of management, include all adjustments which the Company considers necessary for the fair statement of the Condensed Consolidated Results of Operations and Comprehensive Loss and Cash Flows for the interim periods covered and the Condensed Consolidated Financial Position of the Company at the date of the balance sheets. The consolidated financial statements of the Company as at December 31, 2016 included the Company’s accounts and have been prepared in conformity with accounting principles generally accepted in the United States of America (“US GAAP”). The interim results presented herein are not necessarily indicative of the results of operations that may be expected for the full fiscal year ending December 31, 2017, or any other future period. The accompanying unaudited Condensed Consolidated Financial Statements and related financial information should be read in conjunction with the Company’s audited consolidated financial statements and the related notes thereto for the year ended December 31, 2016 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016 filed with the U.S. Securities and Exchange Commission (the “SEC”) on March 13, 2017 (the “Annual Report”).

1. Formation and Business of the Company

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. Our initial focus is on the treatment of heritable cardiomyopathies, a group of rare, genetically-driven forms of heart failure that result from biomechanical defects in cardiac muscle contraction. We have used our precision medicine platform to generate a robust pipeline of therapeutic programs for the chronic treatment of the two most common forms of heritable cardiomyopathy—hypertrophic cardiomyopathy (“HCM”), and dilated cardiomyopathy (“DCM”).

The Company has completed enrollment in a Phase 2 clinical trial of mavacamten (formerly known as MYK-461), our product candidate for the treatment of HCM, and is currently enrolling subjects in a Phase 1 clinical trial of MYK-491, our product candidate for the treatment of DCM. Using our precision medicine development strategy, we believe we have efficiently generated clinical proof of mechanism for mavacamten in both healthy volunteers and in HCM patients, and we intend to pursue a similar path for MYK-491. In 2016, mavacamten was granted Orphan Drug Designation by the U.S. Food and Drug Administration (“FDA”), for the treatment of symptomatic, obstructive hypertrophic cardiomyopathy (“oHCM”), a subset of HCM.

Through September 30, 2017, the Company has financed its operations through an initial public offering (“IPO”), two follow-on public offerings, private placements of redeemable convertible preferred stock and funds received in connection with a license and collaboration agreement with Aventis Inc., a wholly-owned subsidiary of Sanofi S.A., entered into in August 2014 (the “Collaboration Agreement”) (See Note 4). The Company received net proceeds of $93.9 million from the sale of shares of its Series A, A-1 and B redeemable convertible preferred stock. On November 3, 2015, the Company completed its IPO of 6,253,125 shares of common stock at an offering price of $10.00 per share, resulting in net proceeds of approximately $55.6 million, after deducting underwriting discounts, commissions and offering costs. On October 3, 2016, the Company completed a follow-on public offering of 4,370,000 shares of common stock at an offering price of $15.00 per share, resulting in net proceeds of approximately $61.1 million, after deducting underwriting discounts, commissions and estimated offering costs. On August 14, 2017, the Company completed another follow-on public offering of 4,025,000 shares of common stock at an offering price of $35.50 per share, resulting in net proceeds of approximately $133.8 million, after deducting underwriting discounts, commissions and estimated offering costs. In connection with the Collaboration Agreement, the Company has received $105.0 million from Sanofi S.A., consisting of a $35.0 million upfront payment, a $25.0 million milestone payment for the submission of an investigational new drug application (“IND”) for MYK-491 with the FDA in November 2016, and a $45.0 million continuation payment from Sanofi in January 2017. As of September 30, 2017, the Company had an accumulated deficit of $116.4 million and cash and cash equivalents of $227.2 million, short-term investments of $20.0 million and long-term investments of $36.0 million.

The accompanying unaudited Condensed Consolidated Financial Statements, in the opinion of management, include all adjustments which the Company considers necessary for the fair statement of the Condensed Consolidated Results of Operations and Comprehensive Loss and Cash Flows for the interim periods covered and the Condensed Consolidated Financial Position of the Company at the date of the balance sheets. The consolidated financial statements of the Company as at December 31, 2016 included the Company’s accounts and have been prepared in conformity with accounting principles generally accepted in the United States of America (“US GAAP”). The interim results presented herein are not necessarily indicative of the results of operations that may be expected for the full fiscal year ending December 31, 2017, or any other future period.

The accompanying unaudited Condensed Consolidated Financial Statements and related financial information should be read in conjunction with the Company’s audited consolidated financial statements and the related notes thereto for the year ended December 31, 2016 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016 filed with the U.S. Securities and Exchange Commission (the “SEC”) on March 13, 2017 (the “Annual Report”).