Bavencio May Be Effective in Preventing Relapse in Women With Gestational Trophoblastic Tumors

Treatment with Bavencio (avelumab) prevented relapse in women with gestational trophoblastic tumors (GTT) that were resistant to single-agent chemotherapy, according to results of a study presented during the virtual scientific program of the 2020 American Society of Clinical Oncology (ASCO) Annual Meeting.

Results from the small phase 2 study, which is the first trial to explore the use of immunotherapy in patients with GTT, demonstrated that 53% of patients responded to therapy, suggesting that Bavencio may be a new therapeutic option for these patients.

"This proof-of-concept study shows that treatment with the immunotherapy avelumab works against these tumors when resistance to single-agent chemotherapy develops,” said lead study author Dr. Benoit You, of the Centre Hospitalier Lyon-Sud and Lyon Investigational Center for Treatments in Oncology and Hematology in France, in a press release. “Although more evidence is needed before changing clinical practice, these are highly promising results, suggesting that avelumab could prevent patients with chemo-resistant disease from the

severe toxicity of chemotherapy combinations.”

Over the span of two years, 17 patients were enrolled in the trial. Of those, 15 patients were treatable and assessable. Successful normalization of human chorionic gonadotropin (hCG), a hormone produced primarily by certain cells of the placenta during pregnancy, was reached in 53% of patients, leading to discontinuation of Bavencio. There was no sign of disease relapse in any of the patients after 29 months of follow up. Researchers consider patients who reach 12 months disease free with no relapse to be cured.

Patients whose disease was resistant to monochemotherapy (cohort A) or to polychemotherapy (cohort B) received Bavencio intravenously at 10 mg/kg every two weeks. The study drug was administered until hCG normalization, and for three additional cycles thereafter.

The remaining seven patients had a resistance to Bavencio. Those patients were managed with chemotherapy, either with or without surgery.

One patient who reached hCG normalization from the study developed a normal pregnancy and delivered a healthy baby one year after discontinuing treatment.

“This is the first report of a normal pregnancy in a patient previously cured from her tumor with immunotherapy,” said You in pre-recorded presentation. “This provides reassuring data about the impact of immunotherapy on subsequent fertility.”

The investigators reported a satisfactory safety profile for Bavencio, with no severe side effects reported. The most common side effects included fatigue (33%), nausea-vomiting

(33%), infusion-related reactions (27%), thyroid disorder (20%), dry eyes (20%), and diarrhea (20%). One patient reported a uterus bleed, but it was not related to treatment.

GTTs are rare, abnormal growths in the uterus that develop from the placenta during conception and show an overexpression of programmed death-ligand 1 (PD-L1) proteins. Bavencio inhibits PD-L1, making it a reasonable alternative to chemotherapy for patients with these tumors.

The researchers are currently conducting a similar trial for Bavencio in the first-line setting, treating low-risk tumors with methotrexate and Bavencio before resistance can develop. “The objective is to cure 95% of patients,” You said during a press briefing. “With methotrexate, we estimate that we can cure 70% of patients. What we expect is that with the combination with avelumab, we will be able to cure 95% of patients.”