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REPARE THERAPEUTICS Repare Therapeutics Presents Preliminary Phase 1 Monotherapy Clinical Data from the Ongoing First - in - Human Phase 1/2 TRESR Study of RP - 3500 in Solid Tumors at AACR - NCI - EORTC International Conference on Molecular Targets and Cancer Therapeutics October 8 , 2021 Initial TRESR data provide clinical proof of concept and validate Repare Therapeutics ' SNIPRX platform for molecular selection of tumors for therapy with RP - 3500 Favorable and differentiated safety profile , along with promising and distinct early activity , offer clear direction for future development of RP - 3500 Company - sponsored Virtual Webcast Event Today at 5:00 p.m. ET CAMBRIDGE , Mass . & MONTREAL -- ( BUSINESS WIRE ) -- Oct . 8 , 2021-- Repare Therapeutics Inc. ( " Repare " or the " Company " ) ( Nasdaq : RPTX ) , a leading clinical - stage precision oncology company , today announced the presentation of preliminary Phase 1 monotherapy clinical data from its Phase 1/2 TRESR ( Treatment Enabled by SNIPRX ) clinical trial of RP - 3500 , a potent and selective oral small molecule inhibitor of ATR ( Ataxia - Telangiectasia and Rad3 - related protein kinase ) for the treatment of solid tumors with specific synthetic - lethal genomic alterations including those in the ATM gene ( ataxia teleangectasia mutated kinase ) , at the AACR - NCI - EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics . The data are featured today at the AACR - NCI - EORTC conference in an oral presentation titled , " First - in - Human biomarker - driven Phase I TRESR trial of ATR inhibitor RP - 3500 in patients with advanced solid tumors harboring synthetic lethal genomic alterations " ( Abstract number 4950 ) . Preliminary data show that monotherapy RP - 3500 is safe and well tolerated , with compelling early efficacy signals across multiple genotypes and tumor types in heavily pretreated patients . The Company will subsequently host a virtual webcast event today , October 8th at 5:00 p.m. Eastern Time to discuss the latest results from the TRESR trial . " Our initial data for 101 patients treated with RP - 3500 in the ongoing TRESR study resulted in a firm recommendation for Phase 2 dose and schedule , suggest a favorable and differentiated safety profile and provide compelling early evidence of broad clinical efficacy across genotypes predicted by our SNIPRX platform , " said Maria Koehler , MD , PhD , Chief Medical Officer of Repare . " The evolving nature of the data from this ongoing study and specifically the stable tolerability profile and maturing efficacy data offer a clear direction for further development of RP - 3500 . Additionally , we are excited to see that even at this early point in our clinical program , the pharmacokinetic and pharmacodynamic biomarker data already confirm proof- of - mechanism for RP - 3500 in tumors with diverse molecular backgrounds . " " The TRESR study is the largest ever biomarker - selected trial testing single agent ATR inhibitor . We are very pleased that these data suggest RP - 3500 may have a best - in - class profile as a potent and highly selective ATR inhibitor and represent compelling validation for the ability of our SNIPRX platform and our STEP2 process to improve efficacy through molecular selection of tumors , " said Lloyd M. Segal , President and Chief Executive Officer of Repare . " We look forward to the imminent expansion of the TRESR study in a range of genotypes and , continuing and broadening our combination therapy studies , including with a range of PARP inhibitors and gemcitabine . " Key Initial Findings from the TRESR Phase 1/2 Study : TRESR is a first - in - human , multi - center , open - label Phase 1/2 dose - escalation and expansion study , designed to establish the recommended Phase 2 dose and schedule , evaluate safety and pharmacokinetics and identify preliminary anti - tumor activity associated with RP - 3500 , given alone and in combination with talazoparib . The study also examined biomarker responses and their relationship with response to RP - 3500 treatment . Data presented in the abstract reflect the monotherapy cohort at data cutoff of June 4 , 2021 and include 62 patients , while data presented at the conference reflect a data cutoff of August 15 , 2021 and include 101 patients . Highlights from the data presented at the AACR - NCI - EORTC conference include : • RP - 3500 appears safe and well tolerated . The most common treatment emergent adverse events ( TEAE ) in any of the 101 patients treated , expectedly , was grade 1-2 anemia , with only 21.8 % of all patients experiencing Grade 3 anemia ( no Grade 4 ) , and only 14.5 % of those patients treated on the recommended weekly schedule of 3 days on / 4 days off . • There were no discontinuations related to RP - 3500 emergent adverse events and dose interruptions , reductions or red blood cell transfusions were infrequent on the recommended 3 days on / 4 days off regimen . • Recommended Phase 2 dose ( RP2D ) and schedule for further monotherapy RP - 3500 evaluation is 160mg , taken weekly for 3 days on and 4 days off . This schedule assures repeated weekly exposure to RP - 3500 at an efficacious dose . • Antitumor activity was observed in patients with tumors harboring SNIPRX predicted genomic alternations at doses > 100mg ( ATM , CDK12 , BRCA1 , BRCA2 , RAD51B , RAD51C , FZR1 ) , across multiple tumor types and included patients after PARP inhibitor failure . • Meaningful clinical benefit was observed in 49 % of 69 patients with available scans . Those include 12 patients with tumor responses per established international efficacy criteria , 14 patients with ongoing stable disease for at least 16 weeks and 8 patients with stable disease who only had two radiological evaluations , but had demonstrated significant decreases in tumor markers and tumor shrinkage of less than 30 % . • Promising deep molecular responses in circulating tumor DNA ( ctDNA ) for tumors with STEP² genomic alterations were