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Acceleron dealt pipeline setback

Acceleron Pharma canceled further work on experimental drug ACE-083 in a type of muscular dystrophy, after initial results showed it failed to improve patients’ muscular function.The company said the Phase 2 trial showed an improvement in leg and arm muscle volume following treatment, but that did not translate into improvements in patients’ ability to walk or climb stairs. A Phase 2 trial in a second type of degenerative muscular disorder is due to report data in 2020.ACE-083 is Acceleron’s most advanced wholly-owned project. Celgene has licensed blood-disorder treatment luspatercept, due for its first U.S. approval decision in December, and will pay milestones and royalties to Acceleron if successful.

Acceleron has followed a tried-and-true strategy for small biotechs in need of cash for drug development: license a lead project to a bigger company. It sold the rights to luspatercept to Celgene in 2011 in return for R&D funding, equity investment, milestones and royalties greater than 20%.

This allowed Acceleron to independently develop ACE-083, which like luspatercept targets members of a family of proteins called transforming growth factor (TGF) beta. So far, however, Acceleron has had less luck with ACE-083, as it was forced to cancel work in facioscapulohumeral muscular dystrophy (FSHD).

ACE-083 was injected directly into arm and leg muscles, with the belief that it would block TGF beta proteins such as activins and myostatin that inhibit muscle growth. While this approach led to a statistically significant increase in muscle volume, that did not lead to functional improvements as measured by stair-climbing, walking tests or gait analysis.

Another test in a disorder called Charcot-Marie-Tooth syndrome is due to read out in the first quarter of 2020. It has a similar design and endpoints, so the results in FSHD should result in lowered expectations for the second trial.

Meanwhile, the company also expects Phase 2 data from a third experimental drug, called sotatercept, in the first quarter of 2020. Sotatercept had been subject to a Celgene partnership in treating blood diseases like anemia, but Acceleron has regained rights to develop it in pulmonary arterial hypertension, a Phase 2 trial of which is underway.

And the Food and Drug Administration is due to decide in December whether to approve luspatercept for patients with transfusion-dependent beta thalassemia, along with myelodysplastic syndrome, in April 2020.

In the former condition, luspatercept could face competition for some patients next year, as Bluebird bio expects to ask the FDA to approve its gene therapy Zynteglo by the end of 2019.