Bringing an end to a four-year partnership, Sanofi has terminated its agreement with MyoKardia to jointly develop small-molecule therapeutics, targeting genetic mutations associated with certain heart diseases.

MyoKardia will regain full rights to its drug programmes when the deal ends in April, including the experimental drugs mavacamten and MYK-491.

The move was said to not be related to any problems with the company’s clinical data, but rather MyoKardia hesitated at the idea of expanding the Sanofi deal. Consequentially, Sanofi notified MyoKardia of plans to end the pact.

The news comes as MyoKardia prepares to disclose its most significant data yet over the next 24 months; Results from the Phase III EXPLORER study, of mavacamten in hypertrophic cardiomyopathy - a genetic defect that leads to the thickening of heart tissue, irregular heartbeats, and, potentially sudden, fatal strokes in young adults. The results are expected in the second half of 2020.

Over the four years MyoKardia received around $230 million in funding from Sanofi, noting on the break-up that during the period leading up to the end of the research term, it was important for MyoKardia to maintain 100% of the US commercial rights for mavacamten in HCM, as well as additional rights in expanded indications, leading to the eventual demise of the relationship.

MyoKardia chief executive Tassos Gianakakos commented: "Regaining worldwide rights enables us to capture the full value of the data being generated in the next 12-24 months as we prepare for the potential registration of mavacamten in obstructive hypertrophic cardiomyopathy (HCM) and obtain proof-of-concept for MYK-491 in patients with dilated cardiomyopathy.”

Shares in MyoKardia were down as much as about 7% on the news.