Bristol Myers Squibb stock skidded Tuesday — tugging shares of rival Cytokinetics lower — after Bristol's drug, Camzyos, failed in a final-phase study of patients with a devastating heart disease.
The company tested Camzyos in patients with nonobstructive hypertrophic cardiomyopathy, or nHCM. In this condition, the heart muscle thickens, making it harder to pump blood.
After 48 weeks of treatment with Camzyos, patients didn't show improvements on the Kansas City Cardiomyopathy Questionnaire — which assesses the impact of heart failure on patients' lives — nor peak VO2. The latter is how much oxygen the body can use and a sign of heart health.
Bristol Myers Squibb shares declined 2.7% to 49.97. Cytokinetics stock fell 3.1% to 38.56.
How Cytokinetics Is Taking On Bristol Myers Squibb
Cytokinetics is working on a similar drug called aficamten. Both drugs are cardiac myosin inhibitors. They block the myosin protein, which is involved in heart contraction.
RBC Capital Markets analyst Leonid Timashev noted that there are some differences between Camzyos and aficamten. The drugs use different binding sites on the myosin protein. Cytokinetics has also noted aficamten caused fewer side effects in testing than Camzyos.
"On the negative side, we note given the mechanistic similarities, it is possible that the (Camzyos) setback raises concerns that (cardiac myosin inhibitors) do not work in nHCM," he said in a note. "On the positive side, it potentially removes a key competitor in nHCM, leaving aficamten significant green space in this growing indication."
William Blair analyst Matt Phipps says Bristol Myers' press release suggests the company is viewing the obstructive and nonobstructive forms of HCM as different diseases. In obstructive HCM, there is a complete blockage in the heart.
"We believe it is notable that the press release specifically calls out that the results of the studies of (Camzyos) in oHCM and nHCM demonstrate that they are unique diseases, suggesting to us that this was not a 'near-miss' or one in which trends were observed," he said in a report.
Bristol Myers Squibb has estimated nonobstructive HCM represents a third of the total population.
Aficamten's Chances Of Succeeding
Phipps hadn't included nonobstructive HCM in his model for Camzyos, noting the drug didn't show promise in earlier testing.
But Cytokinetics' drug has shown promise in nonobstructive HCM, RBC's Timashev said.
He argued that Bristol Myers Squibb also overenrolled its study. The company had 580 participants and only needed 420 to prove the drug's merit. Cytokinetics enrolled 420 patients in a shorter, 36-week nonobstructive HCM study. Those results are due in 2026.
Timashev believes aficamten is "more likely to work in its own trial." He sees a 70% probability of success for aficamten and has an outperform rating on Cytokinetics stock.
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