Pharmacokinetics and Pharmacodynamics from a First-in-Human Phase 1 Dose Escalation Study with Antagonist Anti-CD40 Antibody, HCD122 (Formerly CHIR-12.12), in Patients with Relapsed and Refractory Chronic Lymphocytic Leukemia.

The CD40 antigen is expressed in most B-cell malignancies, including chronic lymphocytic leukemia (CLL), and represents an attractive target for antibody therapy. HCD122 is a high affinity, fully human IgG₁ antagonistic anti-CD40 monoclonal antibody designed to exert antitumor activity as an inhibitor of CD40-ligand-mediated survival signals and as a potent mediator of antibody-dependent cellular cytotoxicity (ADCC). In this phase 1 study to determine maximum tolerated dose (MTD) in CLL, eligible patients (pts) include those with relapsed or refractory disease after prior fludarabine treatment and are assigned to receive one cycle of 4 weekly infusions of HCD122 at doses ranging from 0.3 to 10 mg/kg depending upon the dose cohort. A standard phase I design is used with each dose cohort enrolling 3–6 pts for evaluation of MTD, toxicity, pharmacokinetics (PK), and pharmacodynamics (PD). To date, 14 pts have been treated at 3 dose levels: 3 pts at 0.3 mg/kg, 4 pts at 1 mg/kg, and 7 pts at 3 mg/kg. Median patient age was 65 yrs (41–74 yrs); median number of prior therapies was 3 (2–11); median WBC at enrollment was 38.8 K/μ L (3.4–284 K/μ L). No dose limiting toxicity (DLT) occurred at the 0.3 and 1 mg/kg dose levels. At 3 mg/kg, streptococcal sepsis was reported in 1 pt after 2 study infusions and was considered DLT. Transient asymptomatic grade 3 or 4 elevation of amylase and/or lipase occurred in 2 subjects. In 9 pts with available data, infusions were associated with manageable grade 1–2 toxicity, primarily chills (7 pts), nausea (4 pts), and fever (3 pts) that was most predominant with the first infusion. PK analysis showed rapid clearance of HCD122 at the 0.3 and 1mg/kg dose levels, with no detectable levels at 2 and 7 days after infusion, respectively. PK data were available from 6 of 7 patients receiving 3mg/kg. These data indicated that some accumulation of HCD122 occurred at this dose level. Complete antigen saturation data were available for 2 of these subjects. Both showed sustained 100% saturation of antigen on peripheral CD5⁺CD19⁺ cells throughout the treatment period. Peripheral CD40+ CLL cells dropped transiently with a mean of 31% during each infusion in the majority of patients but the decreases were not maintained week-to-week. There were no substantive changes in NK or T-cell populations during therapy. In summary, HCD122 was safe and well tolerated up to the 3mg/kg dose level that is currently under evaluation. PK analysis to date suggests that levels higher than 3 mg/kg will be necessary to sustain levels of HCD122 in the expected therapeutic range, and dose escalation will continue to the maximum tolerated dose.