Phase II trial of pharmacodynamically (PDally)-guided optimal biologic dose titration (OBDT) of sorafenib (S) in combination wit

Author(s): M. A. Quintela-Fandino, A. Young, S. Webster, M. Grewal, L. Wang, M. J. Moore, M. Krzyzanowska, T. W. Mak, L. L. Siu; Princess Margaret Hospital, Toronto, ON, Canada; Ontario Cancer Institute, Toronto, ON, Canada

Abstract:

Background: There is a paucity of reliable PD assays for guiding individual OBDT. PD effects of kinase inhibitors have been previously measured in static tissues. We developed a dynamic flow-cytometric PD assay that quantitates RAF signal transduction capacity (STC) based on the differential MEK´s phosphor-status in stimulated vs. basal conditions (phosphor-shift [PS]) in PBMCs. In a pilot study of 7 patients (pt) with advanced solid tumors in a phase I trial (unpublished data) the % of PS inhibition (I) 7 days after starting S at 400 mg BID showed a 10-fold interpatient variation and correlation with TTP. PDGFR-B/VEGFR2 blockade plus mC showed synergistic effect in the RIP1-Tag2 mouse NET model (J Clin Oncol. 23:939) In this phase II trial of aNET a double antiagniogenic strategy is undertaken: PD-guided OBDT of S + mC.

Methods: Eligibility criteria included: unresectable NET with documented PD within 6 months prior to entry; ECOG 0-2; unlimited prior therapy but S; octreotide allowed. Therapy: pt start run-in phase with S at 200mg bid + 50 mg QD fixed dose of mC. After 7 d they escalate to 400 mg BID of S regardless of RAF STC assay results. RAF STC and toxicity are then assessed Q14d, escalating S at 200 mg BID increments until any of the following is achieved: a) 90% RAF STC I; b) maximum S dose of 800 mg BID; or c) intolerable Gr 2 or G3+ toxicity. Once S dose is determined based on these criteria, cycle 1 begins. Design: Simon 2-stage optimal; P0 = 0.05 P1 = 0.2; ? =0.05 ? = 0.1.

Results: Accrual: 10 pt M:F = 6:4, islet cell:carcinoid = 5:5, age median 56 (40-79), ECOG 0:1 = 5:5. S doses (mg BID) at cycle 1 were 200 (2 pt)/400 (5)/600 (2)/800 (1); corresponding cycle 1 day 1RAF STC I (%) were 5, 53/94, 100, 95, 16, 65/25, 41/71, respectively (R² = 0.13 p = 0.72) Most frequent Gr 3 non-hematologic possibly related adverse events in 30 cycles: hand-foot (2 pt), hypertension, abdominal pain, diarrhea, vomiting, lipase, ileal perforation (1 each). Disease control rate (9 evaluable pt): 78% (95% CI: 52-100%) (1PR, 6 SD).

Conclusions: This approach appears feasible/safe. Large interpatient S dose differences are needed to achieve RAF SCT I/toxicity balance. No S dose-RAF SCT I relation is shown. Disease control rate is promising.