Despite a mid-stage miss, Cytokinetics is taking its ALS drug toward Phase III

Cytokinetics CEO Robert Blum

Earlier this year, Cytokinetics ($CYTK) tanked as its lead prospect, a treatment for amyotrophic lateral sclerosis (ALS), missed its primary endpoint and a slew of secondary goals in a mid-stage trial. But the drug did come through on one measure of lung function, and, upon analysis of the results, the biotech believes that could be its ticket to FDA approval.

The treatment, tirasemtiv, is designed to increase muscle sensitivity to calcium, thereby improving movement and functionality in patients with ALS and delaying the disease's characteristic fatigue. However, in a Phase IIb study dubbed BENEFIT-ALS, Cytokinetics' drug failed to significantly improve patient scores on a standardized measure of ALS symptoms, and it posted mixed results on its secondary goals.

But the 711-patient trial wasn't a total loss, the company said, as tirasemtiv charted a statistically significant benefit on patients' slow vital capacity (SVC), which is a measure of how much air they can exhale slowly after a deep breath. After running statistical analyses and consulting with neuromuscular experts, Cytokinetics is convinced improving SVC is a viable surrogate for improving ALS, and the company is now making that case to the FDA, hoping to kick off a late-stage trial on tirasemtiv next year.

"BENEFIT-ALS is the first clinical trial in patients with ALS to demonstrate a positive and potentially clinically meaningful effect on slow vital capacity, an important measure of disease progression and predictor of survival," CEO Robert Blum said in a statement. "We are encouraged by our initial interactions with the FDA relating to the results of BENEFIT-ALS and believe that our continuing discussions can inform our plans to pursue a potential registration program based on effects observed on respiratory function measured by slow vital capacity in patients with ALS."

Investors, however, would seem to be less than optimistic that the FDA will get behind the plan and sign off on SVC as a primary endpoint in Phase III. The latest news sent Cytokinetics' shares up about 6% on Monday, gains that hardly reverse the 65% dive the biotech took after first reporting its Phase IIb results.

Tirasemtiv's mid-stage misstep came on the heels of a setback for Cytokinetics' other lead program, the Amgen ($AMGN)-partnered heart failure treatment omecamtiv mecarbil. An intravenous formulation of the drug failed in Phase IIb, Amgen disclosed last year, and now the Big Biotech is waiting on data from a mid-stage study on an oral version before deciding whether to head into Phase III or scrap the program.

- read the statement