Cytokinetics says early SMA treatment shows promise
- Cytokinetics reported on June 16 that a Phase 2 trial of reldesemtiv, presented at the 2018 Annual Cure SMA Conference, met its objectives of assessing pharmacodynamic effects in spinal muscular atrophy patients, along with safety, tolerability and pharmacokinetics.
- After eight weeks of treatment, adult and adolescent SMA patients had dose- and concentration-dependent increases in time to muscle fatigue as measured by changes from baseline in six minute walk distance (6MWD), and maximal expiratory pressure.
- The results were generally not statistically significant, but the company said the aim of the study was to test its hypothesis. A study investigator called them encouraging, though investors were not so enthusiastic: shares in the company slid 15% Monday morning.
In collaboration with Astellas Pharma, Cytokinetics is developing reldesemtiv as a potential treatment for spinal muscular atrophy and certain other diseases associated with skeletal muscle weakness and/or fatigue. The clinical outcome results from the reldesemtiv study presented were generally not statistically significant, but the company claims the results are supportive of further study.
"We believe that these data support the evaluation of higher doses of reldesemtiv in future clinical trials in SMA given the absence of an efficacy plateau and no dose-limiting safety or tolerability issues," said Fady I. Malik, head of R&D for Cytokinetics, in a statement.
The increases were dose-dependent, but most of the comparisons between treatment and placebo were not statistically significant. Two exceptions were the increase over placebo in 6MWD at week four among patients who received a higher, twice-daily dose of the drug, and a correlation between peak concentration of reldesemtiv and change from baseline in 6MWD.
PTC Therapeutics also presented data at the conference of its experimental drug risdiplam, a potential rival to reldesemtiv and Biogen's marketed Spinraza (nusinersen). Interim data of the FIREFISH Phase 1 study in babies with type 1 SMA showed that more than 90% of the babies studied experienced a greater than 4-point increase in CHOP-INTEND score of motor skills compared with baseline. The babies hit motor milestones and no babies required permanent ventilation.
Risdiplam is in joint development between Roche and PTC, and the second part of that study is ongoing.
Ionis Pharmaceuticals and partner Biogen's Spinraza (nusinersen) won approval in 2016, the first drug cleared in the U.S. for this disorder. Jefferies analyst Michael Yee predicts the potential arrival of risdiplam onto the market could "add to the ongoing uncertainty about durability of the Spinraza 'tail' past 2020+."
Follow Suzanne Elvidge on Twitter