SRRK - Scholar Rock: SMA Data Readout In 2024 Makes This Worth A Look

2023-10-25 17:44:30 ET

Summary

• The Scholar Rock Holding Corporation phase 3 SAPPHIRE study for apitegromab for the treatment of type 2 and type 2 SMA patients has completed enrollment and is expected to report results in Q4 2024.
• Data from the TOPAZ study showed consistent gains in motor function scores for SMA patients treated with apitegromab.
• It is expected that the global spinal muscular atrophy treatment market is projected to reach $8.4 billion by 2032.
• Biomarker and other data from the phase 1 study, using SRK-181 for the treatment of patients with advanced solid tumors, is expected to be released at the Society for Immunotherapy of Cancer 38th Annual Meeting to be held between November 1st to 5th of 2023.

Scholar Rock Holding Corporation ( SRRK ) has been making significant progress in advancing the use of its drug known as apitegromab, which is being developed for the treatment of patients with spinal muscular atrophy [SMA]. This drug is currently being explored in the ongoing phase 3 SAPPHIRE study for the treatment of this patient population.

The company announced that it had completed enrollment for this late-stage study back in September of 2023. It is in line to report top line results from this phase 3 SAPPHIRE study in Q4 of 2024. Data from the open-label TOPAZ study, which used apitegromab for this SMA patient population, was noted to achieve consistent gains in scores of motor functions over a 36-month period. Not only that, but it was noted that more than 90% of non-ambulatory patients remained on the treatment extension study.

Another aspect to consider is that this company is deciding to use this very same drug to treat patients with obesity. It is waiting for receipt of regulatory approval from the FDA so that it could begin a phase 2 proof-of-concept study using apitegromab for this patient population. Should it get the green light to do so, then this would be another shot on goal for apitegromab.

Apitegromab For The Treatment Of Patients With Spinal Muscular Atrophy

The main clinical program in Scholar Rock's pipeline would be the use of apitegromab, which is being advanced in the phase 3 SAPPHIRE study for the treatment of patients with spinal muscular atrophy [SMA]. There is good news to report on this front, because it was announced in September of 2023 that enrollment of this late-stage study had been completed . With completion of enrollment for this trial, it is expected that results from it are going to be released in Q4 of 2024. SAPPHIRE is a randomized, double-blind placebo-controlled phase 3 study, which is evaluating the safety/efficacy of apitegromab for the treatment of nonambulatory patients with types 2 and 3 spinal muscular atrophy [SMA].

However, the goal of this study is not to explore the use of apitegromab alone, but to be given to patients who are already receiving SMN targeted therapy drugs such as nusinersen [SPINRAZA] or risdiplam [EVRYSDI]. This phase 3 trial recruited a total of 156 patients who were randomized 1:1:1 to receive any one of these doses for a 12 month period as follows:

• 10 mg/kg apitegromab
• 20 mg/kg apitegromab
• Placebo.

These doses are to be given to these SMA patients as an intravenous infusion once every 4 weeks. In addition, the company decided to add another exploratory arm into this study. Why is that? That is so that it could explore up to 48 SMA patients who are between the ages of 13 to 21. These patients though are being randomized 2:1 to receive either 20 mg/kg of apitegromab or placebo. The primary endpoint of the SAPPHIRE trial is the "change from baseline in Hammersmith Functional Motor Scale Expanded [HFMSE] total score, which is going to be measured from baseline out to 12 months. The highest score ranges up to 66 points. The higher the score that is achieved, the better the motor function that these type 2 and type 3 SMA patients have.

It's hard to say whether or not the final topline results from the phase 3 SAPPHIRE study will turn out to be positive. However, as I stated above, there was the release of positive results from the 36-month open-label TOPAZ study , which used apitegromab to treat these nonambulatory Type 2 and Type 3 SMA patients ages 2 to 21. It was revealed that there were substantial and sustained gains in both the HFMSE scale I described above and then with respect to another scale known as Revised Upper Limb Module [RULM]. This was all achieved over a 36-month period.

Financials

According to the 10-Q SEC Filing , Scholar Rock had cash, cash equivalents and marketable securities of $249 million as of June 30, 2023. It believed that it would have enough cash to fund its operations into 2025. However, it chose not to wait to enact a cash raise and chose to do so recently. Back on October 16th of 2023 it closed an underwritten public offering . It sold 14,270,074 shares of common stock, along with the exercise in full by the underwriters' option to purchase an additional 1,861,314 shares at the offering price to the public of $6.85 per share. In total, it was able to generate $97.8 million in gross proceeds from this offering, before expenses. This newly added cash should extend its cash runway beyond the originally planned expectation of being able to fund itself into 2025.

Risks To Business

There are several risks that investors should be aware of before investing in Scholar Rock. The first risk to consider would be with respect to the ongoing phase 3 SAPPHIRE study, which is using apitegromab for the treatment of patients with type 2 and type 3 SMA. That's because even though this drug was shown to exhibit substantial and sustained improvement in the phase 2 open-label TOPAZ study, there is no guarantee that the drug will beat placebo in the phase 3 SAPPHIRE study.

A second risk to then consider would be with respect to the possible regulatory filing if the primary endpoint is met with statistical significance. That's because the FDA will still have to review safety/efficacy data of apitegromab for the treatment of these SMA patient populations. There is no assurance that the FDA will approve this drug, nor that it will reach the market.

A third risk to consider would be with respect to the use of apitegromab for the treatment of patients with obesity. This biotech is waiting for regulatory clearance from the FDA so that it can begin a phase 2 proof-of-concept study using this drug for the treatment of this patient population. There is no guarantee that the agency will grant such requested approval, nor that a phase 2 study for this program will happen.

Conclusion

Scholar Rock Holding Corporation has made great progress in being able to advance its drug apitegromab for the treatment of patients with type 2 and type 3 spinal muscular atrophy [SMA]. The goal is to not directly compete with current therapies, because this drug is being given to these SMA patients in addition to their current SMN targeted therapies. The belief is that the addition of apitegromab, which may have disease-modifying properties, might provide a boost for these patients who are already receiving such SMN targeted therapies. There is a huge market opportunity for any biotech working on spinal muscular atrophy for sure, and there is a chance that Scholar Rock Holding Corporation might be able to capture a good chunk of it.

It is expected that the global spinal muscular atrophy treatment market is projected to reach $8.4 billion by 2032 . Not only does this company have potential to go after this indication, but as I highlighted above, it also has an opportunity to use apitegromab to go after the obesity market as well. Hopefully it receives its clearance to begin a phase 2 study proof-of-concept study using this drug to treat this patient population.

Lastly, it is in the process of advancing another candidate in its pipeline known as SRK-181, which is being developed to treat patients with advanced solid tumors. It is expected that biomarker and other data from the phase 1 study , using this drug to treat advanced solid tumor patients, are going to be released at the Society for Immunotherapy of Cancer [SITC] 38th Annual Meeting in San Diego, to be held between November 1st to 5th of 2023.

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