Phase 1/2 study evaluating the safety and efficacy of DSP‐7888 dosing emulsion in myelodysplastic syndromes

DSP‐7888 is an immunotherapeutic cancer vaccine derived from the Wilms’ tumor gene 1 (WT1) protein. This phase 1/2 open‐label study evaluated the safety and efficacy of DSP‐7888 dosing emulsion in patients with myelodysplastic syndromes (MDS). DSP‐7888 was administered intradermally (3.5 or 10.5 mg) every 2 weeks for 6 months and then every 2‐4 weeks until lack of benefit. Twelve patients were treated in phase 1 (3.5 mg, n = 6; 10.5 mg, n = 6), with no dose‐limiting toxicities reported. Thus, the 10.5 mg dose was selected as the recommended phase 2 dose, and 35 patients were treated in phase 2. Forty‐seven patients received ≥1 dose of the study drug and comprised the safety analysis set. The most common adverse drug reaction (ADR) was injection site reactions (ISR; 91.5%). Grade 3 ISR were common (58.8%) in phase 1 but occurred less frequently in 2 (22.9%) following implementation of risk minimization strategies. Other common ADR were pyrexia (10.6%) and febrile neutropenia (8.5%). In the efficacy analysis set, comprising patients with higher‐risk MDS after azacitidine failure in phases 1 and 2 (n = 42), the disease control rate was 19.0%, and the median overall survival (OS) was 8.6 (90% confidence interval [CI], 6.8‐10.3) months. Median OS was 10.0 (90% CI, 7.6‐11.4) months in patients with a WT1‐specific immune response (IR; n = 33) versus 4.1 (90% CI, 2.3‐8.1) months in those without a WT1‐specific IR (n = 9; P = .0034). The acceptable safety and clinical activity findings observed support the continued development of DSP‐7888 dosing emulsion.