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That key Gilead breast cancer readout? Try 2024, and don’t get your hopes up: analyst

Gilead Sciences just tipped off what sounded like mixed results for Trodelvy, the cornerstone of the Big Biotech’s oncology ambitions. Now, one analyst suggests investors continue to keep their expectations low for the key expansion opportunity⁠—at least for now.

After coming short of declaring a clinically meaningful benefit for Trodelvy in stalling cancer progression or death in patients with pretreated HR-positive, HER2-negative breast cancer, Gilead is probably focusing on a final analysis of gold-standard patient survival data, RBC Capital Markets analyst Brian Abrahams said in a Tuesday note after speaking with Gilead’s investor relations team. That analysis is due in 2024.

Although the current phase 3 clinical trial, dubbed TROPiCS-02, could yield another analysis of whether Trodelvy can extend patients’ lives over chemo toward the end of this year or early 2023, the final readout “can better inform regulators of the potential benefit/risk for Trodelvy,” Abrahams said.

Still, it remains unclear just how much of an improvement in overall survival in this breast cancer population is clinically meaningful, Abrahams said; that topic will need to be hashed out with regulators. The TROPiCS-02 trial was powered for a death risk reduction of 27% of a median overall survival of 16.5 months for Trodelvy and 12 months for chemo, Mizuho analyst Salim Syed noted in a report Monday.

“Our sense is that the Street should continue to maintain low expectations” for Trodelvy’s data and regulatory path in HR-positive, HER2-negative breast cancer, Abrahams said.

Trodelvy, an anti-TROP2 antibody-drug conjugate, is the crown jewel of Gilead’s $21 billion acquisition of Immunomedics in 2020 and a key component in the company’s goal to receive a third of its 2030 revenues from oncology products. After approvals in triple-negative breast cancer and bladder cancer, the potential expansion into HR-positive, HER2-negative breast cancer has become an important measure to gauge Trodelvy’s pan-tumor potential

Now, after Gilead implied a light showing on disease progression, Trodelvy may face a smaller-than-expected—or lost—third-line HR-positive, HER2-negative breast cancer opportunity, Abrahams added. Gilead will likely take a write-down for the Immunomedics buy, he said.

If Trodelvy were eventually successful in this third-line setting—which Abrahams figured is only 40% likely—it could open up $900 million in peak worldwide sales, the RBC analyst said in a Monday note.

Trodelvy did deliver a statistically significant improvement over chemotherapy in progression-free survival, according to Gilead. But because the TROPiCS-02 trial was designed to detect a small difference for statistical significance, investors have been on the lookout for a clinical meaningful readout.

Given the timing, the full TROPiCS-02 data could be presented at the upcoming American Society of Clinical Oncology annual meeting in June, Abrahams projected. Investors will also keep a close eye on any data from AstraZeneca and Daiichi Sankyo’s rival anti-TROP2 antibody-drug conjugate, datopotamab deruxtecan (DS-1062).

In the meantime, Gilead “sounded very committed” to exploring Trodelvy in earlier line HR-positive, HER2-negative breast cancer but didn’t lay out specific timing, Abrahams said. As Gilead noted, most of the more than 20 oncology clinical trials it plans to start this year include Trodelvy.