Abstract LB_A12: Initial results from 2 Phase I studies of NMS-03305293, a selective PARP1 inhibitor
Authors: Geurts Marjolein , Gramatzki Dorothee , Merler Sara , Duca Matteo , Girardi Fabio , Sener Ugur T. , Roberti Domenico , Saturno Grazia , Crivori Patrizia , Montagnoli Alessia , Mahnke Lisa , Fu Siqing , Gaviani Paola , Jaeckle Kurt A. , Zhang Jian , Shi Yehui , Guarneri Valentina , Weller Michael , Kizilbash Sani H. , Bent Martin J. van den , Milella Michele , Damian Silvia 
Published: December 2023

Background PARP-1 has a well-established role in DNA repair.  PARP-1 selective inhibitors are a new subclass of PARPi that offer potential for improved tolerability. NMS-03305293 (NMS-293) is an oral, brain-penetrant PARP-1 selective inhibitor with strong antitumor activity in BRCA mutated preclinical models.  Furthermore, NMS-293 is synergistic with temozolomide (TMZ) in glioblastoma mouse models.

Methods Two phase I/I-II dose-escalation/expansion studies assessed safety, tolerability, and preliminary antitumor activity of NMS-293.  Both are actively recruiting. In PARPA-293-001 (NCT04182516), NMS-293 was administered orally, ranging from 20 mg (QD) to 160 mg (BID) for 21 or 28 days on 28-day cycle in adult patients with advanced/metastatic, relapsed/refractory solid tumors who have exhausted standard treatment options. In PARPA-293-002 (NCT04910022), NMS-293 was administered in a range of doses orally, QD or BID on days 1-7 plus TMZ 150mg/m2 QD on days 1-5 in repeated 28-day cycle in adult patients with recurrent diffuse gliomas. Tumor responses were measured by investigator-assessed RANO criteria.

Results The unpooled safety database at the data-cut-off (02-AUG-23), includes 45 patients in PARPA-001 and 21 patients in PARPA-002. PARPA-001 showed an MTD of 100 mg BID for 28 days on a 28-day cycle, a dose with meaningful PK relative to preclinical activity. PARPA-002 dose finding is ongoing with no DLTs as of cutoff date. The most frequent (≥10%) any-grade treatment related adverse events (TRAEs) in PARPA-001 were reversible QTcF prolongation, nausea, asthenia, decreased appetite and vomiting, mainly mild/moderate. In PARPA-002, with discontinuous NMS-293 plus TMZ, no G≥3 TRAEs were reported.  The most frequent (≥10%) any-grade TRAEs were: nausea, fatigue, vomiting, decreased appetite, and platelet count decreased, mainly G1 adverse events. Overall, no dose-dependent trends of myelosuppression have been observed. 14 recurrent glioma patients across dose levels in PARPA-002 were evaluable for tumor response.  A patient with glioblastoma had confirmed partial response (PR) with duration 7.6+ weeks, remaining on treatment at cutoff date. A patient with grade 3 IDH-mutant astrocytoma had unconfirmed PR with ongoing tumor shrinkage at 16.1+ weeks. A patient with glioblastoma had complete radiological disappearance of enhancing non-target lesions, remaining on treatment at cutoff date. NMS-293 PK profiles showed an increase in exposure with the dose with approximately 5 to 13 hours half-life.

Conclusion NMS-293, a PARP-1 selective, brain penetrant inhibitor was well tolerated in phase I clinical trials with no dose dependent trends of myelosuppression. Furthermore, NMS-293 showed encouraging clinical activity in combination with TMZ in difficult-to-treat recurrent glioma patients.

Citation Format: Marjolein Geurts, Dorothee Gramatzki, Sara Merler, Matteo Duca, Fabio Girardi, Ugur T. Sener, Domenico Roberti, Grazia Saturno, Patrizia Crivori, Alessia Montagnoli, Lisa Mahnke, Siqing Fu, Paola Gaviani, Kurt A. Jaeckle, Jian Zhang, Yehui Shi, Valentina Guarneri, Michael Weller, Sani H. Kizilbash, Martin J. van den Bent, Michele Milella, Silvia Damian. Initial results from 2 Phase I studies of NMS-03305293, a selective PARP1 inhibitor [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr LB_A12.