AstraZeneca PLC saw its shares weaken on Thursday after an external expert panel advising the U.S. Food and Drug Administration voted against backing the company's investigational breast cancer medicine camizestrant.
By 07:37 GMT the stock had retreated 1.6% in London.
The FDA's Oncologic Drugs Advisory Committee delivered a 6 to 3 vote that did not support the risk-benefit profile of camizestrant, which AstraZeneca has been developing as a first-line option for a subtype of breast cancer driven by a particular genetic mutation. The panel determined the therapy failed to show a "meaningful benefit" for patients whose disease had not progressed on existing treatment.
Although advisory committee recommendations are not legally binding on the agency, the FDA often follows their guidance. A final regulatory decision from the agency is expected at a later date.
Analysts at Morgan Stanley, led by Sarita Kapila, said the panel's negative vote creates "regulatory overhang and a dent to investor sentiment." They added: "We see a decreased likelihood of approval in the SERENA-6 setting following the 6-3 negative ODAC vote, though approval remains possible."
AstraZeneca responded to the vote by saying it was "disappointed" with the outcome while reiterating confidence in its trial data and in the drug's potential to benefit patients.
The data presented from clinical trials showed camizestrant delayed disease progression by more than six months. When used in combination with other cancer medicines, the treatment produced a median progression-free survival of 16 months versus 9.2 months for patients receiving the current standard of care.
Market participants and investors will now await the FDA's formal decision, which the agency is expected to issue later. Until that determination, the advisory panel's recommendation and analyst concern over approval odds are likely to weigh on sentiment toward AstraZeneca shares and related biotech equities.
Impacted sectors include pharmaceutical and biotech companies engaged in oncology drug development, as well as broader equity markets sensitive to regulatory news in healthcare.