Relay Therapeutics' combo therapy cuts breast cancer progression in early study

[September 10, 2024]  By Mariam Sunny and Sneha S K

(Reuters) -Relay Therapeutics said on Monday interim data from an early-stage study of its combination drug for breast cancer showed it meaningfully extended the time patients lived without the disease worsening, sending shares surging about 37% in early trading.

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 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.

Astra's combination drug Truqap, approved for use in these patients, had helped improve the time patients with gene-altered tumors lived without their disease worsening by 7.3 months.

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 U.S., according to American Cancer Society.

A doctor exams mammograms in Nice, France January 4, 2008. REUTERS/Eric Gaillard/file photo

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.

In 2019, Novartis' Piqray became the first approved PI3K inhibitor.

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 said.

If successful, Schmidt estimates U.S. peak sales of about $1.5 billion for the drug in second-line treatment of breast cancer.

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)

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