CTNI-44. A PHASE 0 'TRIGGER' TRIAL OF PAMIPARIB IN NEWLY DIAGNOSED AND RECURRENT GLIOBLASTOMA PATIENTS. (14th November 2022)

• Record Type: Journal Article
• Authors: Sanai, Nader; Chang, Yu-Wei; Jiang, Jun; Molloy, Jennifer; Montgomery, Chelsea; Harmon, Jocelyn; Hong, Amy; Wanebo, John; Kennedy, William; Garcia, Michael; Barani, Igor; Yoo, Wonsuk; Tovmasyan, Artak; Tien, An-Chi; Li, Jing; Mehta, Shwetal
• Is Part Of: Neuro-oncology. Volume 24(2022)Supplement 7
• Page Start: vii82
• Page End: vii82
• Publication Date: 2022-11-14
• Subjects: Brain Neoplasms -- Periodicals; Brain -- Tumors -- Periodicals; Brain -- Cancer -- Periodicals; Nervous system -- Cancer -- Periodicals; 616.99481
• DOI: 10.1093/neuonc/noac209.309
• Languages: English
• ISSNs: 1522-8517

Abstract

Abstract: This study evaluates glioblastoma (GBM) pharmacokinetics (PK) and pharmacodynamics (PD) of pamiparib, a PARP1/2-selective inhibitor, graduating patients to a therapeutic expansion phase of drug plus radiotherapy. Newly-diagnosed (Arm A) and recurrent GBM (Arm B) patients received 4 days of pamiparib (60 mg BID) prior to planned resection at 2-4 or 8-12 hours following the final dose. Arm C included recurrent GBM patients who received 4 days of olaparib (200 mg BID). Tumor tissue cerebrospinal fluid (CSF), and plasma were collected. Total and unbound drug concentrations were measured using validated LC-MS/MS methods. A PK 'trigger', defined as unbound drug > 5-fold biochemical IC50 in nonenhancing tumor determined eligibility for the therapeutic expansion phase. PARP inhibition was assessed via ex vivo radiation and quantification of PAR levels compared to non-radiated control. All patients exceeding the PK threshold were eligible for an expansion phase of study drug plus radiotherapy followed by maintenance regimen. In Arms A (n = 20) and B (n = 15), the mean unbound concentrations of pamiparib in Gd-nonenhancing tumor region were 171.5 nM and 102.9 nM, respectively and in Arm C (n = 4) the mean unbound concentration of olaparib was 11.0 nM. All patients in Arms A and B, but only one in Arm C, exceeded the PK threshold to qualify for the expansion phase of the study. 12/20 (60%), 7/14 (50%), and 1/4 (25%) patients in Arms A, B, and C, respectively progressed to expansion phase. Radiation-induced PAR expression was 2.44 fold in untreated control vs 1.16 in Arm A, 0.82 in Arm B and 1.11 in Arm C patients, respectively. The median progression-free survival was 5.4 (Arm A) (n = 7), 5.0 months (Arm B) (n = 6), and 2.7 months (Arm C) (n = 1), respectively. Pamiparib was generally well-tolerated, achieved pharmacologically-relevant concentrations in nonenhancing GBM tissue and suppressed induction of PAR levels ex vivo post-radiation.