2556 Background: Depletion of tumor-infiltrating CD25+ regulatory T cells (Tregs), which inhibit tumor-specific immune responses, could contribute to tumor eradication. Cami (ADCT-301), an anti-CD25, pyrrolobenzodiazepine-based antibody-drug conjugate, targets CD25+ Tregs. A mouse surrogate has shown potent antitumor activity in solid tumor models. Here we report preliminary data from the monotherapy arm of a phase 1b trial of Cami in pts with selected advanced solid tumors. Methods: The monotherapy dose-escalation part of this open-label study enrolled pts (aged ≥18 years) with selected advanced solid tumors and no suitable existing therapy. The primary objective was to characterize safety and tolerability, and to identify the recommended phase 2 dose of Cami monotherapy. Secondary and exploratory objectives included evaluation of preliminary antitumor activity, pharmacokinetics (PK), pharmacodynamics (PD), and immunogenicity. Pts received Cami every 3 weeks (1 cycle) with dose escalation per a 3+3 design. Disease control rate (DCR) was assessed (complete and partial responses [CR, PR] and stable disease). Results: At data cut-off (Dec 17, 2020), 44 pts were enrolled, with primary tumor types (stage IVA/B: 27 pts; 61.4%) of colorectal (15 pts; 34.1%), pancreatic (14 pts; 31.8%), head and neck, ovarian/fallopian tube, and renal cell carcinoma (all 3 pts; 6.8%), non-small cell lung cancer (2 pts; 4.5%), gastric, esophageal/GEJ, melanoma, and triple-negative breast cancer (each 1 pt; 2.3%). Median (range) age was 60.5 (33–82) years; median (range) number of prior systemic therapies was 4 (1–9). Pts received a median (range) of 2 (1–6) Cami cycles at doses of 20–150 µg/kg. Median (range) treatment duration was 22 (1–178) days. No dose-limiting toxicities were reported. The maximum tolerated dose (MTD) was not reached. All-grade treatment-emergent adverse events (TEAEs) in ≥20% pts were nausea (18 pts; 40.9%), decreased appetite and fatigue (each 16 pts; 36.4%), constipation (13 pts; 29.5%), abdominal pain (11 pts; 25%), and rash (10 pts; 22.7%). The only Grade ≥3 TEAE in ≥10% pts was anemia (5 pts; 11.4%). Grade 3 autoimmune AEs (colitis, immune-mediated AE, systemic inflammatory response syndrome) and neurologic AEs (dysphagia and asthenia, but not GBS) were reported in 3 (6.8%) and 2 (4.5%) pts, respectively. 1 (2.3%) Cami-related TEAE led to treatment withdrawal; no Cami-related TEAEs were fatal. DCR was 25% (95% CI: 11.1, 34.7); 11/44 pts attained stable disease. No pts had CR or PR. Conclusions: Dose escalation of Cami monotherapy is complete. The safety profile is encouraging and MTD was not reached. PK/PD data will be presented. 150 µg/kg is the highest dose investigated for single-agent Cami and the highest to be investigated combined with pembrolizumab in selected advanced solid tumors in the current protocol. Funding: ADC Therapeutics SA NCT03621982. Clinical trial information: NCT03621982.
Correction: Phase 1A/1B dose-escalation and -expansion study to evaluate the safety, pharmacokinetics, food effects and antitumor activity of pamiparib in advanced solid tumours
