Garrett, Gerald

Abstract Purpose: CD4 T-cell immunity is associated with improved survival in patients with breast cancer. We previously reported a phase I trial evaluating a folate receptor alpha (FRα) vaccine administered with cyclophosphamide (CP), demonstrating excellent safety and immunogenicity. To simplify the vaccine strategy for ease of use, we report here the results of a randomized phase II trial evaluating a lower vaccine dose alongside the original dose, administered with or without CP pretreatment. Patients and Methods: Patients with triple-negative breast cancer who completed all systemic and local therapies were assigned to receive either low-dose (825 μg) or high-dose (2.5 mg) vaccine peptides plus GM-CSF in six 4-week cycles, with or without CP prior to vaccination. Safety was monitored, and immunogenicity was evaluated before and after vaccination. Results: A total of 80 patients were dosed with vaccine, and 58 patients were evaluable for immunogenicity. Vaccination was well tolerated and elicited immunity in 83% of patients. Levels of FRα-specific T cells were high, persistent, and comparable with T-cell levels against tetanus toxoid. No differences in immunity were observed between the two doses. CP pretreatment also did not affect the immune responses. Recurrences occurred in eight evaluable patients and were unrelated to the treatment arm. No patients died during the study because of their disease. Conclusions: The reduced-dose FRα vaccine is as effective as the original dose and does not require CP to generate maximal immunity. These findings may inform the design of trials testing efficacy in triple-negative breast cancer or other cancers.

6040 Background: FRα is overexpressed on > 90% of high-grade EOC. We conducted a randomized double-blind multicenter phase II clinical trial to evaluate the safety and efficacy of TPIV200 (a multi-epitope FRα peptide vaccine admixed with GM-CSF adjuvant) versus GM-CSF alone as a control in patients with stage III-IV high-grade platinum-sensitive epithelial ovarian, fallopian tube, or primary peritoneal carcinoma in first complete or partial remission, irrespective of baseline level of FRα expression. Methods: Patients with stage III-IV high-grade serous, high-grade endometrioid, carcinosarcoma or poorly differentiated EOC who had previously completed standard upfront therapy without evidence of disease progression and who were within a year of last platinum were randomized 1:1 to intradermal vaccination of TPIV200 versus intradermal GM-CSF alone. The vaccination period included 6 administrations of the study drug at 4-week intervals. Up to 6 booster vaccinations at 12-week intervals were permitted for patients who did not have disease progression. AEs were assessed using CTCAE. Tumor response was assessed via RECIST every 12 weeks. The primary endpoint, progression free survival (PFS), was calculated from date of first vaccination to the date of progression, death or study termination. Results: Of 120 patients randomized, 63 (53%) were treated on the TPIV200 arm. The median age at study entry was 63 years (range 37-88). AEs were generally mild. Injection site reaction was more frequent in the TPIV200 (63%) versus GM-CSF arm (39%). The other most common AEs, abdominal pain (25%) and fatigue (23%), were comparable in both arms. At study termination with a median follow-up of 15.2 months (range: 1.2-28.3 months), 68 of 119 intention-to-treat patients had progressed (55% in the TPIV200 arm and 59% in the GM-CSF arm). The median PFS was 11.1 months (95% CI: 8.3-16.6 months) and there was no statistically significant difference in median PFS between the arms (10.9 months with TPIV200 versus 11.1 months with GM-CSF, HR = 0.85 [upper 90% CI = 1.17]). Conclusions: Although TPIV200 had a manageable safety profile, the study was terminated for futility after the planned interim analysis. Future development of FRα-targeted therapy will likely focus on the careful selection of patients whose cancers show high FRα expression. Clinical trial information: NCT02978222.