- Scholar Rock, a biopharmaceutical company based in Cambridge, Massachusetts, plans to sometime this year test its most important experimental drug in a clinical trial that could provide the evidence needed to ask for approval.
- The drug, called apitegromab, is being studied as a potential treatment for spinal muscular atrophy, a rare, genetic disease that causes muscles to weaken and diminish. Scholar Rock on Tuesday announced results from a trial of almost 60 patients, showing those who were given apitegromab generally seemed to improve on certain scales used to measure the severity of the disease.
- While Scholar Rock claims these results show its drug works, there are still important unanswered questions. For example, almost all patients in the trial were receiving apitegromab along with an approved SMA therapy known as Spinraza. It's therefore not yet clear what type of benefit Scholar Rock's drug provides on its own, and how long any benefit will last.
The treatment of SMA has advanced dramatically over the last five years. Before, there were no medicines to slow the disease's progression. But that changed in 2016 with the approval of Biogen's Spinraza, which works by boosting production of a protein critical to many cellular and body functions.
Since then, two more options have become available in Zolgensma, a gene therapy approved in 2019, and Evrysdi, an oral drug approved last year. Like Spinraza, Zolgensma and Evrysdi spur the body to make more of that critical protein, called survival motor neuron or SMN. All three of these treatments have been show to slow or even stabilize disease, although their price tags make them among the most expensive therapies on the market.
For drug developers, the next big advance would be to find ways to further improve SMA patients' motor function. Scholar Rock is betting apitegromab can do just that, and is using the data released Tuesday to make its case.
Apitegromab doesn't work like the currently marked SMA therapies. Instead, it targets a protein known to inhibit muscle cell growth. Scholar Rock's trial tested the drug across three groups of SMA patients who differed based on age, the severity of their disease and when they first started receiving treatment.
In the first group, patients were 5 to 21 years of age, able to walk and had the most mild form of SMA, known as Type 3. These patients were given apitegromab either by itself, or in conjunction with Spinraza. Scholar Rock noted that while the collective group ended up having a 0.3-point average decline on an SMA severity scale, the majority of the patients maintained or improved their motor function.
The second group were 5 to 21 years of age as well, but they could not walk and had the more moderate, Type 2 form of disease. These patients had started treatment with Spinraza at five years old or older. In the study, the group demonstrated an average 0.6-point improvement on a different scale used to measure SMA severity.
The last group were at least 2 years old, had Type 2 SMA, and began Spinraza treatment before they turned 5. Using the same scale as the second group, these patients demonstrated an average 7.1-point improvement when treated with a 20 milligram per kilogram dose of apitegromab and a 5.3-point improvement when given a lower, 2 milligram per kilogram dose.
Speaking with investors Tuesday, Scholar Rock executives said these results support the idea that apitegromab could provide an "additive therapeutic benefit" for a variety of SMA patients. They also believe the drug could have applications in other neuromuscular diseases, including Duchenne muscular dystrophy and Becker muscular dystrophy.
The company said it's planning a "proof-of-concept" clinical trial in Becker's that it aims to launch in 2022.
"As progress is made in the development of next generation, disease-stabilizing therapies, we believe apitegromab could have potential as an add-on to help improve motor function, and we remain committed to exploring this potential in the near term," said Ted Miles, Scholar Rock's chief financial officer, on the Tuesday call.
Investors don't appear sold on the fresh data or Scholar Rock's strategy, it seems, as the company's share price was down by about 15% Tuesday morning.