RG6206 (talditercept alpha, anti-myostatin adnectin), formerly BMS-986089, is a myostatin inhibitor originally developed by Bristol-Myers Squibb and later licensed to Roche. It is currently being investigated as a therapy for Duchenne muscular dystrophy (DMD) but is not yet approved by the U.S. Food and Drug Administration or the European Medicines Agency.

How RG6206 works

Like most cells, muscle cells or myocytes divide to form new cells or regenerate worn-out muscle tissue. The muscle cell division process occurs in multiple stages starting from the myoblasts that finally differentiate into myocytes. Myostatin, also known as growth differentiation factor 8 (GDF 8), is an inhibitor that prevents the differentiation of myoblasts into myocytes, hindering muscle growth so that muscles do not grow too large.

People with DMD show symptoms of low muscle mass and muscle wasting. RG6206 binds to myostatin and prevents it from acting on muscle tissue. This helps the muscle tissue to grow and differentiate. Scientists think that inhibiting myostatin in these people using therapeutics such as RG6206 can help increase muscle mass.

RG6206 in clinical trials

A Phase 1 randomized single and multiple-ascending dose study (NCT02145234) of RG6206 was completed in February 2016. The study found that RRG6206 was well-tolerated in DMD patients who could still walk. The treatment also helped in increasing thigh muscle mass and total lean body mass.

A Phase 1 open-label randomized clinical trial (NCT03100630) to study the safety and efficacy of RG6206, and to compare its bioavailability when injected under the skin in the arm, thigh, and abdomen in healthy adults was completed in 2017. This trial showed good tolerability of RG6206. 

A Phase 1/2 multi-site randomized clinical trial (NCT02515669) to evaluate the safety and efficacy of multiple ascending doses of RG6206 injected under the skin in DMD patients that are still able to walk is currently ongoing but no longer recruiting participants. The results of the trial are expected to be available in August 2020.

A Phase 2/3 clinical trial (NCT03039686) called SPITFIRE to further assess the safety, efficacy, and tolerability of RG6026 is currently recruiting boys, age 6 to 11, with DMD, who can still walk. The results of the trial are expected to be available in December 2024.

Other information

Pfizer was also developing a myostatin inhibitor called domagrozumab (PF-06252616), but it was discontinued in August 2018 as patients recruited for the clinical trial (NCT02310763) testing it were not showing significant improvements in muscle function.

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