An Open-Label, Phase 1 Study of R-CVP in Combination with Inotuzumab Ozogamicin in Patients with CD22-Positive B-Cell Non-Hodgkin's Lymphoma: Preliminary Safety and Efficacy Data

Inotuzumab ozogamicin (INO) is a humanized anti-CD22 antibody conjugated to calicheamicin, a potent antitumor antibiotic. CD22 is expressed on the majority of B-cell non-Hodgkin's lymphomas (NHL). This phase 1 study was conducted to identify the maximum tolerated dose (MTD) of INO when given in combination with R-CVP (rituximab 375 mg/m², cyclophosphamide 750 mg/m², and vincristine 1.4 mg/m² all on Day 1 and prednisone 40 mg/m²on Days 1–5) every 21 days, and to obtain preliminary safety and efficacy data for this regimen.

The study enrolled patients with relapsed/refractory CD22+ B-cell NHL. The dose-escalation part (Part 1; previously presented) identified the MTD as INO 0.8 mg/m² given on Day 2 with R-CVP q3wks [Blood. 2011;118:3715]. Subsequent cohorts included the MTD confirmation cohort (Part 2) and MTD expansion cohort (Part 3), for collection of additional safety and preliminary efficacy data. Untreated patients who were not candidates for anthracyclines were allowed in Part 2 and Part 3 of the study. In Part 2 (n = 10), confirmation of the MTD required a dose-limiting toxicity (DLT) rate of <33% in Cycle 1 and fewer than 1/3 of patients discontinuing prior to Cycle 3 due to an adverse event (AE). In Part 3 (n = 22), additional patients were enrolled to explore preliminary signs of activity of INO when given in combination with R-CVP.

In Parts 2 and 3, a total of 32 patients with follicular lymphoma (FL; n = 15), diffuse large B-cell lymphoma (DLBCL; n = 16), or mantle cell lymphoma (n = 1) were enrolled. CD22 expression was confirmed by immunohistochemistry or flow cytometry prior to enrollment. The median age was 65 years (range, 44–81 years); 34% of patients had 1 prior anti-lymphoma regimen, 34% had 2, 28% had ≥3, and 3% (n = 1) had no previous therapy (median, 2; range, 0–6). The median number of cycles received was 5 (range, 1–6).

In Part 2, the MTD was confirmed as standard-dose R-CVP plus INO 0.8 mg/m², with 2 of 10 patients presenting with a DLT (grade 3 increase in alanine/aspartate aminotransferases [ALT/AST] and grade 4 neutropenia requiring granulocyte-colony stimulating factor). Four patients discontinued due to AEs after 2 cycles (n = 1), 3 cycles (n = 2), and 5 cycles (n = 1), respectively.

Across Parts 2 and 3, the most common treatment-related AEs (all grades) were thrombocytopenia (78%), neutropenia (66%), fatigue (53%), constipation (50%), leukopenia (50%), and nausea (41%); the most common grade 3/4 AEs included neutropenia (63%), thrombocytopenia (53%), leukopenia (38%), lymphopenia (31%), increased ALT (9%), increased AST (6%), and febrile neutropenia (6%). There was 1 case of treatment-related fatal pneumonia associated with grade 4 neutropenia. Ten patients discontinued study treatment due to AEs, with thrombocytopenia or delayed recovery from thrombocytopenia being the leading AE causing study drug discontinuation (n = 9 [grade 1/2, n = 6; grade 3/4, n = 3]).

The best overall response (ORR; partial + complete response [CR]) from Part 2 and 3 (31 evaluable patients) was 77% (n = 24/31), including 29% (n = 9/31) with CR. Of patients with FL, the ORR was 100% (n = 15/15), including 53% (n = 8/15) with CR. Of patients with DLBCL, the ORR was 60% (n = 9/16), including 7% (n = 1/16) with CR.

Results from this phase I study showed that R-CVP in combination with INO 0.8 mg/m² may have acceptable toxicity and promising activity in patients with relapsed or refractory CD22+ B-cell NHL, based on the response rates in FL and DLBCL. The most common grade 3/4 AEs were hematological toxicities, notably thrombocytopenia and neutropenia. Follow-up for progression-free survival and overall survival is currently ongoing; however, the observed results warrant additional study in both indolent and aggressive B-cell NHL.

Ogura:Pfizer Inc: Research Funding. Hatake:Pfizer Inc: Research Funding. Davies:Pfizer Inc: Research Funding. Crump:Pfizer, Celgene, Roche, Millennium, Seattle Genetic: Membership on an entity's Board of Directors or advisory committees. Tobinai:Merck, Zenyaku, Symbio, Biomedics, Pfizer, GSK, Chugai/Roche: Research Funding. Smith:Pfizer Inc: Research Funding. Offner:Pfizer Inc: Research Funding. Wang:Pfizer Inc: Employment, Equity Ownership. Ishibashi:Pfizer Inc: Employment, Equity Ownership. Paccagnella:Pfizer Inc: Employment, Equity Ownership. Vandendries:Pfizer Inc: Employment, Equity Ownership. MacDonald:Roche Canada: Membership on an entity's Board of Directors or advisory committees, Research Funding.