Abstract
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Objectives: To determine the maximum tolerated dose (MTD), dose-limiting toxicity and clinical response of patients (Pts) with ATL to 90Y-HAT. Previously we demonstrated that 90Y-labeled murine anti-Tac (CD25) produced responses in ATL but HAMA production limited treatment. HAT, a humanized monoclonal antibody to CD25, eliminates this risk and was expected to produce superior clinical benefits.
Methods: Eligibility: ATL with ≥10% CD25+ cells or serum soluble-Tac >1,000 U/mL, ANC>1,000/mm3, Plt.>75,000/mm3, adequate hepatic/renal function and informed consent. The Phase I dose escalation study started at 15mCi 90Y-HAT and increased by 5 mCi in each cohort until MTD. 111In-labeled HAT was co-administered for tumor imaging. To reduce marrow exposure to free 90Y, Ca DTPA was infused for 3 days. Treatments were administered every 6 weeks if the ANC >1500/mm3, Plt. >100,000/mm3 and no disease progression.
Results: 20 Pts., median age 43 years (range, 27-68), 8 males, 12 females, 17 with prior treatment, received a median of 1 cycle (range, 1-9). In the initial 8 Pts. bone marrow suppression limited treatment. The study was amended so only the first dose was escalated in each cohort, and subsequent treatments got 5mCi 90Y-HAT. Twelve additional patients were treated. Dose-limiting thrombocytopenia occurred at 30mCi 90Y-HAT and the MTD was 25mCi. Toxicities were mostly hematological: grade 3/4 granulocytopenia- 12 Pts. (60%), thrombocytopenia- 9 Pts. (45%), and anemia- 3 Pts. (15%). One Pt. had tumor lysis syndrome requiring intensive care support. Localization of 111In-HAT at tumor sites was seen. There were 2 CRs (5 and 32 mo) and 7 PRs (2, 2, 4, 5, 6, 8 and 16 mo). Phase II enrolled 9 Pts., median age 52 years (range, 34-74), 5 males, 4 females, 6 with prior treatment. A total of 12 cycles were administered. Only 3 Pts. received a second dose. One Pt. achieved a PR (6 weeks). Grade 3/4 neutropenia was seen in 6 Pts. (67%), thrombocytopenia in 3(34%), and anemia in 1(11%). One Grade 3 mucositis was the only significant non-hematological toxicity. Median survival on Phase II was 4.75 months (range, 1-99+).
Conclusions: The MTD of 90Y-HAT therapy in ATL was 25 mCi. There was a 45% response rate in Phase I but only a single short duration response in Phase II. The response rate with 90Y-HAT was not improved compared with 90Y labeled murine anti-Tac.
Research Support (if any): This research was supported by the Intramural Research Program of the NIH
- Society of Nuclear Medicine, Inc.