Retreatment Protocol for BL22 Immunotherapy in Relapsed or Refractory Hairy Cell Leukemia

Study Summary

BL22 is a type of protein that scientists have created to interact with certain cancer cells. Experiments have shown that BL22 can bind with cancer cells that have a particular kind of protein (called CD22 ) on their surface, and can kill those cells. CD22 is present on certain types of hairy cell leukemia (HCL) cancer cells, and researchers have been working on treatments that will use BL22 and other related proteins to interact with and kill these kinds of cancer cells. The primary purpose of this study will be to provide access to and treatment with BL22 for patients who have HCL in order to determine their response to the treatment. In addition, the study will assess potential side effects of BL22 and examine why some patients respond better than others to treatment with BL22 and related therapies. This study will include about 21 to 25 adults who have been diagnosed with forms of HCL that have not responded well to standard treatments such as surgery, chemotherapy, or radiation therapy. These adults also will have received anti-CD22 therapies before, potentially including treatments with BL22, and have not developed immunity or resistance to these treatments. Prior to the study, patients will undergo a 1- to 2-week screening period to assess their eligibility for treatment. Eligible patients will participate in the study for up to 16 cycles of treatment, with each cycle lasting approximately 4 weeks. For each cycle, patients will receive 1 prescribed dose of BL22 every other day for a total of 3 doses per cycle, and will be assessed after every cycle to evaluate the success of the treatment. During the evaluation visits, patients will be required to have a brief physical examination, give blood and urine samples for testing, and undergo other tests as need to check heart and kidney function and assess the state of the leukemia. Patients who agree will give additional blood, urine, or bone marrow samples for future research purposes.

Primary Outcome

Response is defined by the Response Evaluation Criteria in the protocol, namely the earliest point where all relevant tests (i.e. lab tests, physical exam, radiology results) are consistent with complete response (CR) or partial response (PR). CR or PR must be confirmed for at least 4 weeks. Complete response: No evidence of leukemic cells by routine H/E stains of the peripheral blood and bone marrow. Partial response:neutrophils \>/= 1,500/micrograms/L or 50% improvement over baseline without g

Interventions

• DRUG BL22 (CAT-3888)