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Lower motor neurons of the spinal cord are the main cell type affected by SMA. When the lower motor neurons deteriorate, they no longer efficiently contact their target muscles. This leads to loss of voluntary muscle contraction, which causes muscle wasting, or atrophy, due to inactivity.

The goal of muscle protection is to defend the muscles from atrophy, increase muscle mass, and perhaps even restore some muscle function. Similar to neuroprotection, this strategy does not address the underlying genetic cause of SMA, rather, the aim is to slow or stop the progression of the condition.

The muscle protection treatments currently being tested in clinical trials are all being delivered in combination with an SMN-dependent therapy (e.g., nusinersen or risdiplam. In addition, all of them work by inhibiting myostatin, a protein that naturally restricts muscle growth. For further details, please see this page.


14th March: Biohaven Pharmaceuticals announced they had received Fast Track designation from the U.S. Food and Drug Administration (FDA) for Taldefgrobep alfa.

4th January: Biohaven Pharmaceuticals, had initiated RESILIENT, a Phase 3 combination trial of Taldefgrobep alfa and was recruiting participants in the USA.


Roche announced that it will initiate MANATEE, a new global Phase 2/3 clinical study to evaluate the safety and efficacy of GYM329 (RO7204239).


2nd December: Scholar Rock announced the design of SAPPHIRE Trial of Apitegromab.

7th July: Scholar Rock received Fast Track Designation in the US from the FDA for Apitegromab which added to its orphan drug status.


28th October: Scholar Rock reported on interim results from their TOPAZ (Apitegromab) clinical trial.

3rd August: Catalyst, biopharmaceutical company announced a randomised, double-blind, placebo-controlled outpatient study, designed to evaluate the safety, tolerability and efficacy of amifampridine phosphate in ambulatory, nusinersen-naïve patients diagnosed with SMA Type 3. The study enrolled 12 SMA Type 3 patients (both male and female patients), aged between 6 and 50 years in sites in Italy and Serbia.

(Update Jan 2023: Catalyst is no longer pursuing the possible use of amifampridine phosphate treatment for SMA)


25th November: Scholar Rock reported preliminary data from TOPAZ Phase 2 trial (Apitegromab).

18th March: Scholar Rock announced positive interim results from TOPAZ Phase I trial in healthy volunteers of their lead compound, SRK-015 (Apitegromab).


4th December: Scholar Rock announced that their experimental drug for SMA, SRK-015 (Apitegromab) had been designated as an Orphan Drug status for SMA in the European Union.

Scholar Rock also recently published some pre-clinical data on the effects of an early-generation variant of SRK-015, called SRK-015P, in SMA mouse models.

The work, was published in the peer-reviewed scientific journal Human Molecular Genetics and showed that co-administration of SRK-015 with a drug that increases SMN levels called SMN-C1 provided greater benefit than SMN-C1 treatment on its own.

20th June: Cytokinetics presented data at the 2018 Cure SMA conference from the Phase II clinical trial with SMA patients of its drug CK-2127107, which had been renamed reldesemtiv. Cytokinetics was primarily testing reldesemtiv in diseases causing neuromuscular dysfunction, weakness and fatigue, to see whether it can improve muscle function and physical performance.

(Update Jan 2023: Catalyst is no longer pursuing the possible use of reldesemtiv treatment for SMA)

3rd May: Scholarock announced that the US Food and Drug Administration (FDA) granted Scholar Rock Orphan Drug Designation to SRK-015 (Apitegromab )for the treatment of SMA.


25th May: has announced that the US Food and Drug Administration (FDA) has granted Orphan Drug Designation to its compound CK-2127107 for the potential treatment of SMA.


11th January: Cytokinetics and Astellas began enrolling SMA patients in a Phase II clinical trial of their muscle-activating drug, CK-2127107 (reldesemtiv).