J Clin Oncol 31, 2013 (suppl; abstr 8602)
Irene M. Ghobrial, Jacob Laubach, Philippe Armand, Erica Boswell, Courtney Hanlon, Stacey Chuma, Esther Dawn Chu, Damian Handisides, Stew Kroll, Barbara Hickingbottom, Kenneth Carl Anderson, Paul Gerard Guy Richardson; Dana-Farber Cancer Institute, Boston, MA; Jerome Lipper Multiple Myeloma Center, Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA; Threshold Pharmaceuticals, Inc., South San Francisco, CA; Threshold Pharmaceuticals, South San Francisco, CA
Background: TH-302 is an investigational 2-nitroimidazole prodrug of the DNA alkylator Br-IPM designed to be selectively activated in hypoxia. In multiple myeloma (MM) mouse models, diseased animals demonstrate a marked expansion of areas of hypoxia in the bone marrow. TH-302 exhibited anti-tumor activity against MM in vitro and in vivo and synergism was seen when combined with bortezomib (Hu et al, Blood 2010; Chesi et al, Blood 2012). Based on these findings, a phase I/II study of TH-302 plus dexamethasone (dex) was initiated for patients (pts) with relapsed/refractory MM.
Methods: Eligible pts in the study (NCT01522872) had ECOG PS ≤ 2, receipt of at least two prior therapies, and acceptable hepatorenal function and hematologic status. A standard 3+3 dose escalation design was used with a fixed oral 40 mg dose of dex and 40% dose increments of TH-302. TH-302 was administered IV with dex on days 1, 4, 8, and 11 of a 21-day cycle. The objectives were to determine DLTs and the MTD; assess the safety, tolerability and preliminary clinical activity of TH-302 plus dex; and study the relationship between hypoxia within the bone marrow and response to TH-302.
Results: Eleven pts have been treated: 7M/4F with a median age 61 years (range: 53 – 86) and 6 prior therapies (range: 3 – 10). All received both bortezomib and lenalidomide/thalidomide containing regimens. TH-302 was dosed at 240 (n=5), 340 (n=4), and 480 (n=2) mg/m² for a median of 5 cycles. No DLTs were reported at 240 or 340 mg/m². Two pts treated at 480 mg/m² had DLTs of grade 3 mucositis, exceeding the definition of MTD. A dose expansion is thus ongoing at 340 mg/m2. Two patients had SAEs related to TH-302 (pneumonia). Five pts continue on study after a median of 7 cycles (range: 2–11). Nine pts have had efficacy evaluations: 2 pts with partial responses, 2 pts with minimal responses, and 5 pts with stable disease, for an overall response rate (of MR or better) of 44%.
Conclusions: TH-302 can be administered at 340 mg/m2 biweekly + dex, with dose limiting mucositis seen at higher doses. Initial clinical activity has been noted with an ORR of 44% in heavily pretreated MM pts who are relapsed/refractory to both bortezomib and lenalidomide.
Clinical trial information: NCT01522872