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Subcutaneous injections of low doses of veltuzumab (humanized anti-CD20 antibody): Objective responses in B-cell malignancies.

8530 Background: Low IV doses of veltuzumab, a second-generation anti-CD20 monoclonal antibody with structure-function differences from chimeric rituximab, have shown clinical activity, thus justifying subcutaneous (SC) injections.


METHODS
A phase I/II study was initiated in patients (pts) with previously untreated or relapsed CD20+ indolent NHL or CLL who received 4 SC injections of veltuzumab 2 weeks apart at dose levels of 80, 160, or 320 mg. Efficacy was assessed by CT-based IWG (NHL) or hematology-based NCI/IWCLL (CLL) criteria 4 and 12 weeks later, with responding pts continuing follow-up. Other evaluations included AEs, safety laboratories, B-cell blood levels (CD19), serum veltuzumab levels, and human anti-veltuzumab antibody (HAHA) titers.


RESULTS
Nineteen pts (8M/11F, median age 63), including 14 NHL pts (11 follicular, 3 other indolent NHL; 5 treatment naive) most with stage III or IV disease (11/14) and 5 CLL pts (4 treatment naïve) all with Rai stage II or III disease, have now received SC veltuzumab at 80 mg (3 NHL, 3 CLL), 160 mg (9 NHL, 2 CLL) or 320 mg (2 NHL) dose levels. Pre-treatment with antihistamines or steroids has not been required, and SC veltuzumab was well tolerated with only mild, transient injection site reactions and tenderness. To date, all HAHA results have been negative. In NHL pts, SC veltuzumab demonstrates good bio-availability, with a slow release pattern over several days and depletion of circulating B cells starting after 1st injection. Initial response information is currently available for 10 pts. For 7 NHL pts, 4 weeks after treatment with 80 or 160 mg doses, 2 pts had partial responses, 3 pts showed stable disease, and 2 pts had disease progression. For 3 CLL pts who received 80 mg doses, serum veltuzumab levels were lower, but all pts still achieved 65-75% decreases in circulating leukemic cells over the course of treatment.


CONCLUSIONS
SC administration of veltuzumab is well tolerated, achieves slow but efficient delivery into the blood, and is pharmacologically active. The low doses currently evaluated in B-cell malignancies show evidence of therapeutic activity, achieving objective responses in NHL and notable reductions in circulating leukemic cells in CLL. [Table: see text].