Phase I and Pharmacokinetic Study of Inotuzumab Ozogamicin (CMC- 544) as a Single Agent in Japanese Patients with Follicular Lymphoma Pretreated with Rituximab.

Introduction: Inotuzumab ozogamicin (CMC-544) is an antibody-targeted chemotherapeutic agent composed of a monoclonal antibody which targets the CD22 antigen, conjugated to calicheamicin, a potent cytotoxic antitumor antibiotic. Since CD22 is expressed on more than 90% of B-lymphoid malignancies, CMC-544 may be useful for treating patients (pts) with B-cell non-Hodgkin lymphoma (B-NHL). In a phase I study in the US and EU, CMC-544 showed definite clinical activity in pts with relapsed/refractory B-NHL (both follicular and diffuse large) with clinically manageable thrombocytopenia as the main toxicity. In this phase 1 study, the safety, tolerability, efficacy and pharmacokinetics (PK) of CMC-544 was evaluated in Japanese pts with relapsed or refractory B-cell NHL.

Methods: CMC-544 was administered IV once every 28 days ± 2 days (1 cycle). A dose escalation was planned using 1.3 mg/m² and 1.8 mg/m², the maximum tolerated dose (MTD) which was previously determined in non-Japanese pts. Pts were allowed to enroll in the study if they had relapsed or refractory CD22+ B-NHL. Tumor responses were evaluated by investigator’s assessment according to the International Workshop Criteria for NHL.

Results: Enrollment for this study is complete and included 13 pts (6 women, 7 men, median age [range] of 49 yrs [43–72]). All of the 13 pts who were enrolled had follicular lymphoma and had received at least one regimen of rituximab alone or rituximab-containing chemotherapy in their prior treatments. The median number of prior treatment regimens was 1 (range: 1–13). In dose escalation, no pts had dose limiting toxicities and the tolerability in the MTD previously determined in non-Japanese pts (1.8mg/m²) was confirmed for Japanese pts. 3 pts and 10 pts were treated with 1.3 mg/m² and 1.8 mg/m² of CMC-544, respectively. The median number of CMC-544 treatment cycles was 3 (range: 2–8). The most common drug-related adverse events (AEs, all grades ≥ 35% pts) included thrombocytopenia (100%), leukopenia (92%), neutropenia (85%), elevated AST (85%), anorexia (85%), lymphopenia (85%), nausea (77%), elevated ALT (54%), malaise (46%), and headache (46%). Grade 3/4 AEs ≥ 15% pts were: thrombocytopenia (54%), lymphopenia (31%), neutropenia (31%), and leukopenia (15%). 7 pts discontinued treatment due to AEs; 1 pt because of grade 2 rash, 1 pt because of grade 2 urticaria and 5 pts because of AEs which required treatment delays of >3 wks (2 pts with prolonged thrombocytopenia, 1 pt with prolonged thrombocytopenia and neutropenia, 1 pt with neutropenia and elevated alkaline phosphatase, and 1 pt with prolonged neutropenia and elevated total bilirubin). PK analyses demonstrated that maximum serum concentration (C_max) and area under the curve (AUC) of CMC-544 increased in a dose dependent manner. Both parameters increased with the second dose in the second cycle. At all dose levels, terminal half-life (t_1/2) was prolonged, and total clearance (CL) was decreased in the second cycle. Overall, the PK profile was similar to that of the previous study with non-Japanese pts. 7 pts had CRs (CR + CRu), 4 pts had PRs, and 2 pts had stable disease. The objective response rate (ORR) was 85% (11/13).

Conclusions: The tolerability of CMC-544 for Japanese pts with relapsed or refractory follicular B-NHL who had been pretreated with rituximab was confirmed at 1.8 mg/m² administered once every 28 days. This is the same dose level as the MTD for non-Japanese pts. The PK profile of CMC-544 in Japanese pts was similar to that in non-Japanese pts. Based on the acceptable safety profiles and a high preliminary ORR, CMC-544 should be considered for further investigations in Japanese pts with relapsed or refractory B-NHL who have been pretreated with rituximab.