205 Background: Phase I and II single dose 177Lu−J591 studies have been published. Based on the theoretical advantages of dose fractionation on safety and efficacy, we initiated a phase I dose−escalation study of fractionated−dose 177Lu−J591. Methods: Men with progressive mCRPC with normal neutrophil and platelet counts were enrolled. The initial portion was 3+3 dose−escalation, with 6 cohorts of 3−6 patients receiving 2 doses 177Lu−J591, 2 weeks apart starting with 20 mCi/m2, escalating to 45 mCi/m2. After determining maximum tolerated dose (MTD), patients enrolled in 2 expansion cohorts at recommended phase II doses (RP2D). Planar imaging of 177Lu−J591 at 6−8 days following the initial dose was performed. Pre− and post−treatment PSA was measured for all patients and the highest dose−level cohorts had CTC counts (CellSearch) measured before and after treatment. Results: 48 patients enrolled with median age 74 (55−95) ), median baseline PSA 45.38 (1.93−766.5), 37.5% with prior chemo. The RP2D’s of fractionated 177Lu−J591 were 40 mCi/m2 or 45 mCi/m2 x2 with option for GCSF. Overall PSA decline ≥ 50% in 9 (18.8%), ≥ 30% in 14 (29.2%) and any PSA decline in 26 (54.2%); at RP2D doses (n = 32), 8 (25%) with ≥ 50%, 12 (37.5%) with ≥ 30%, and 20 (62.5%) with any PSA decline. Of 25 with available CTC counts, 14 declined, 8 remained stably favorable, and 3 increased. Of 12 with unfavorable baseline CTC counts, 8 (66.7%) became favorable at follow up, 2 decreased by 30% and 88% but remained ≥ 5, and 2 increased; 1 converted from < 5 to ≥ 5. Thirty-five (72.9%) had grade 3/4 hematological toxicities; 19 (59.4%) with Gr 4 heme toxicity in RP2D cohorts, with 15 (16.9%) receiving at least 1 platelet transfusion, 6 receiving GCSF, and 0 with febrile neutropenia. Overall 4 had Gr 1 transaminitis and 14 (29.2%) had grade 1 infusion reactions (without pre−medication). Accurate targeting of 177Lu−J591 at known sites of disease seen in 84.4%. Conclusions: Fractionated 177Lu−J591 is well tolerated with predictable, reversible myelosuppression, achieving a higher cumulative dose than possible with a single dose. Both PSA and CTC count control was achieved. Clinical trial information: NCT00538668.
Treatment of Advanced Pancreatic Carcinoma with 90Y-Clivatuzumab Tetraxetan: A Phase I Single-Dose Escalation Trial
