When Gilead Sciences report Earlier this year, its drug Trodelvy met the primary goal of a pivotal study in a specific population of breast cancer patients, but it provided few details. The company is now reporting some additional numbers, but it’s unclear whether they’ll be enough to support the blockbuster expectations for the drug, which is at the heart of a multibillion-dollar acquisition.
Trodelvy is conducting a phase 3 test in patients with HR-positive and HER2-negative breast cancer who have already received several early-stage treatments — patients who are very sick and have a poor prognosis.Gilead Sciences at the American Society of Clinical Oncology Annual Meeting in Chicago came up with On Saturday, preliminary analysis of the pivotal study showed that the drug helped patients survive an average of five-and-a-half months without the cancer progressing or causing death. While the nearly 6-month benefit was encouraging, it was only 6 weeks longer than the median 4 months for patients receiving chemotherapy.
This reduced the risk of disease progression, or death, by 34 percent, enough to meet the primary learning goal, Hope Rugo, professor of medicine and director of breast oncology and clinical trials education at UCSF and principal investigator of the clinical trial, said in the abstract. The jury is still out on overall survival, or how long patients live after treatment. Gilead said the first interim analysis of this key secondary endpoint showed an improving trend, but the data were immature. The study will continue to follow patients for this overall survival analysis.
Gilead’s drug has indeed achieved the main goal of its research, Véronique Dieras, an oncologist at the Marquis de Eugene Center in Rennes, France, said in an abstract introduction to Trodelvy and others. But while the 5.5-month versus 4-month progression was statistically significant, she said it was unclear whether the results were clinically meaningful and led to better quality of life.
“Maybe my underlying concern is that when we look at the results of the phase 3 studies, we have to ask about the magnitude of the benefit and whether it’s clinically meaningful,” she said. “What we saw in this study was only a 1.5-month difference between the two arms. We may need more data. What effect will it have on overall survival — the data are not yet mature.”
HR-positive/HER2-negative breast cancer is the most common type of breast cancer, with nearly 400,000 people diagnosed worldwide each year. Gilead said in announcing the Trodelvy results that the cancer can spread, and when it does, the survival rate drops to around 30 percent in the absence of other causes of death. When this cancer becomes resistant to hormone-based therapy, the primary treatment option is one chemotherapy followed by another. Due to the toxic effects of chemotherapy, the response to this approach will decline, as will the patient’s quality of life.
Trodelvy is an antibody-drug conjugate, a drug that links a targeted antibody to an anticancer drug payload. By targeting the drug to cancer cells, the goal is to limit the toxic effects in healthy tissue. Trodelvy’s antibody component targets TROP 2, a protein on the surface of many solid tumors, including about 80 percent of breast cancers.
In terms of safety, the phase 3 trial of Trodelvy in HR-positive/HER2-negative breast cancer was consistent with earlier studies. Compared with chemotherapy, the most common grade 3 or higher treatment-related adverse reactions included low levels of type A white blood cells, diarrhea, anemia, and fatigue.
Immunomedics, the original developer of Trodelvy, turned it to FDA approves triple-negative breast cancer in 2020, a rare but more aggressive form of breast cancer. After a few months, Gilead agrees to pay $21 billion to buy ImmunomedicsUnder Gilead, the drug has become a moderate seller, with $380 million in sales last year. Expanding the drug’s approval to include HR-positive/HER2-negative breast cancer is seen as key to driving sales into blockbuster territory.
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