ATR inhibitor, camonsertib, dose optimization in patients with biomarker-selected advanced solid tumors (TRESR study)

Elisa Fontana*, Ezra Rosen, Elizabeth K Lee, Martin Højgaard, Niharika B Mettu, Stephanie Lheureux, Benedito A Carneiro, Gregory M Cote, Louise Carter, Ruth Plummer, Devalingam Mahalingam, Adrian J Fretland, Joseph D Schonhoft, Ian M Silverman, Marisa Wainszelbaum, Yi Xu, Danielle Ulanet, Maria Koehler, Timothy A Yap

*Corresponding author for this work


BACKGROUND: Camonsertib is a selective oral inhibitor of ataxia telangiectasia and Rad3-related (ATR) kinase with demonstrated efficacy in tumors with DNA damage response gene deficiencies. On-target anemia is the main drug-related toxicity typically manifesting after the period of dose-limiting toxicity evaluation. Thus dose/schedule optimization requires extended follow-up to assess prolonged treatment effects.

METHODS: Long-term safety/tolerability and antitumor efficacy of three camonsertib monotherapy dose levels/schedules were assessed in the TRESR study dose-optimization phase: 160 mg once daily (QD) 3 days on/4 off (160 3/4; the preliminary recommended phase II dose [RP2D]) and two step-down groups of 120 mg QD 3/4 (120 3/4) and 160 mg QD 3/4, 2 weeks on/1 off (160 3/4, 2/1w). Safety endpoints included incidence of treatment-related adverse events (TRAEs), dose modifications, and transfusions. Efficacy endpoints included overall response rate, clinical benefit rate, progression-free survival, and circulating-tumor-DNA (ctDNA)-based molecular response rate.

RESULTS: The analysis included 119 patients: 160 3/4 (n = 67), 120 3/4 (n = 25), and 160 3/4, 2/1w (n = 27) treated up to 117.1 weeks as of the data cutoff. The risk of developing grade 3 anemia was significantly lower in the 160 3/4, 2/1w group compared with the preliminary RP2D group (HR = 0.23, 2-sided P = .02), translating to reduced transfusion and dose reduction requirements. The intermittent weekly schedule did not compromise antitumor activity.

CONCLUSION: The 160 3/4, 2/1w dose was established as an optimized regimen for future camonsertib monotherapy studies offering significantly reduced anemia incidence without any compromise to efficacy.

Original languageEnglish
JournalJNCI-Journal of the National Cancer Institute
Publication statusE-pub ahead of print - 6 May 2024


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