Pharmacokinetics of Tarlatamab, a Delta-Like Ligand-3 (DLL3) Targeted Half-Life Extended Bispecific T-Cell Engager (BiTE®) Immunotherapy in Adult Patients with Previously Treated Small-Cell Lung Cancer: Results from DeLLphi-300, a Phase I Multiple-Dose-Escalation Study.

Background: Tarlatamab binds to delta-like ligand 3 on cancer cells and cluster of differentiation-3 on T cells, leading to T-cell-mediated tumor lysis, and has demonstrated a promising safety and efficacy profile in patients with previously treated small-cell lung cancer (SCLC). Here, we present pharmacokinetic results from DeLLphi-300 (NCT03319940), an ongoing international, open-label, first-in-human study in previously treated adult patients with SCLC.

Methods: Multiple escalating doses of tarlatamab were administered every 2 weeks (Q2W; 0.003, 0.01, 0.03, 0.1, 0.3, 1, 3, 10, 30, and 100 mg) in a 28-day cycle. To reduce the risk of cytokine-release syndrome, starting at the 3 mg dose level, a step dose regimen was employed consisting of a 1 mg infusion on cycle 1 day 1 (C1D1), followed by the target dose on C1D8, C1D15, and Q2W thereafter. All doses were infused over 1 h. Other tarlatamab dosing regimens were also explored, either for patient convenience (every 3 weeks) or to mitigate cytokine-release syndrome (extended intravenous infusion over a period of 3 days). Intensive pharmacokinetic samples were collected during cycles 1 and 2, and additional samples for pharmacokinetic and immunogenicity measurement were collected at regular intervals in later cycles. Pharmacokinetic data were analyzed using noncompartmental analysis, and antidrug antibody (ADA) incidence, including any effect on tarlatamab pharmacokinetic parameters, was summarized.

Results: Pharmacokinetic data were available from 203 patients. The median age was 62 years (range 32-80), and 55.7% (n = 113) of patients were male, 78.3% (n = 159) were white, and 8.3% (n = 17) were of Japanese descent. Following intravenous infusion, serum tarlatamab concentrations declined with time in a biphasic manner. Serum exposures increased in an approximately dose-proportional manner across the evaluated target dose range with a mean (standard deviation) estimated terminal phase elimination half-life of 5.8 (1.6) days, and steady state achieved by approximately C2D15. Of the 183 evaluable patients, 12 (6.6%) developed treatment-emergent ADAs; the distribution of dose-normalized serum concentrations were similar between patients who were ADA positive and ADA negative. In addition, the distribution of exposures was comparable in Japanese and non-Japanese patients.

Conclusion: In patients with previously treated SCLC, tarlatamab demonstrated dose-proportional pharmacokinetic and extended half-life characteristics that support a Q2W dosing interval. Neither Japanese race nor ADA had a clinically relevant impact on exposures.