An accelerated approval for Gilead Sciences’ cancer drug Trodelvy could be in question after the company disclosed Thursday afternoon that a confirmatory trial failed to meet its main objective.

In the trial, called TROPiCS-04, Trodelvy did not significantly extend survival versus chemotherapy among people with locally advanced or metastatic bladder cancer. Gilead noted the data numerically favored Trodelvy and pointed to smaller groups of study participants that showed positive trends, however.

The company also reported that, across the overall study population, there were more deaths due to adverse events among people given Trodelvy than there were among those on chemo. The deaths were mainly reported early on in treatment and tied to complications from low counts of a type of white blood cell. Trodelvy, which was conditionally cleared for bladder cancer by the Food and Drug Administration in 2021, carries a safety warning for this risk, known as neutropenia.

Gilead plans to further study the deaths and said it would reiterate to physicians that supporting treatment should be given to prevent neutropenic complications.

The company said it will present full study data at an upcoming meeting. But, according to analysts, the outcome could jeopardize Trodelvy’s conditional approval for previously treated bladder cancer.

“We believe that [Gilead’]s Trodelvy will likely lose its FDA-labeled indication for metastatic urothelial carcinoma, or bladder cancer, following the disappointing topline overall survival miss for TROPiCS-04,” wrote Leerink Partners analyst Daina Graybosch, in a client note Thursday.

Michael Yee, an analyst at Jefferies, took a similar view, writing that the negative results “put in question” if Trodelvy’s bladder cancer indication will be withdrawn.

The drug’s 2021 approval was granted by the FDA based on earlier study data detailing Trodelvy’s ability to shrink tumors. The OK is contingent on “verification and description of clinical benefit in confirmatory trials, including the TROPiCS-04 study,” Gilead said.

The trial miss is another setback to Gilead’s development of Trodelvy, which it acquired via a $21 billion buyout of Immunomedics in 2020. Earlier this year, results from another Phase 3 study showed the drug didn’t significantly extend survival among people with previously treated lung cancer, when compared to a common chemo treatment.

On Friday, Gilead released further details of the lung cancer study, results from which will be presented at the American Society of Clinical Oncology’s annual meeting. Treatment with Trodelvy reduced the relative risk of death versus chemotherapy by 16%, but the difference did not surpass the statistical threshold to declare the trial a success. The risk reduction reflected a 1.3-month difference in median overall survival between the two study groups.

Gilead noted that, among study participants whose tumors didn’t respond to their last immunotherapy, there was a more meaningful improvement in median overall survival of 3.5 months. While this analysis was prespecified, it was not set up for formal statistical testing.

Trodelvy is not approved for the treatment of metastatic lung cancer. In addition to its bladder cancer indication in the U.S., the drug is also available in multiple countries for two types of advanced breast cancer.

According to Leerink’s Graybosch, bladder cancer accounts for less than 10% of Trodelvy’s total sales, which were about $310 million over the first three months of 2024. An antibody-drug conjugate, the treatment has been a major part of Gilead’s expansion into oncology.

Gilead shares fell by 2.2% at market open Friday, before gaining back some of those losses by mid-morning.