By Mariam Sunny and Sneha S K
(Reuters) – Relay Therapeutics said on Monday interim data from an early-stage study of its experimental combination treatment for breast cancer showed it meaningfully extended the time patients lived without their disease worsening.
The main goal of the trial, which enrolled 118 heavily pre-treated patients with PI3K mutant, advanced breast cancer, was to test the safety and tolerability of the combination therapy.
The treatment, RLY-2608, in combination with AstraZeneca’s Faslodex, was generally well tolerated across all doses, the company said.
It helped 52 patients live for an average of 9.2 months without the disease worsening after treatment in the study.
But two patients out of 64, who received a 600 milligram dose of the combination, discontinued the treatment due to related side effects, including itching and nausea, while one experienced severe hyperglycemia or high blood sugar.
Breast cancer is the second-most common cancer and the second-leading cause of cancer death among women in the United States, according to American Cancer Society.
The therapy selectively targets a type of protein called PI3K, a mutation of which affects more than one in three people with breast cancer in the U.S., according to the company.
Current treatment options include Novartis’ Piqray and AstraZeneca’s Truqap. Roche is testing its experimental drug, inavolisib, in late-stage studies.
Piqray is “quite toxic and has a lot of side effects and it’s very poorly tolerated by patients”, Guggenheim analyst Michael Schmidt had said ahead of the interim data.
“At the end of the day, we look for … better safety and better activity compared to, for example, drugs like Novartis’ Piqray,” Schmidt added.
If successful, Schmidt estimates potential U.S. peak sales of about $1.5 billion for the drug in second-line treatment of breast cancer.
Astra’s combination drug Truqap had helped improve the time patients with gene-altered tumors lived without their disease worsening by 7.3 months.
Relay plans to start a late-stage trial for the combination next year, pending regulatory discussions.
(Reporting by Mariam Sunny and Sneha S K in Bengaluru; Editing by Shilpi Majumdar)
