On June 3, 2023 Cyteir Therapeutics, Inc. ("Cyteir") (Nasdaq: CYT), a clinical stage oncology company, reported results from a Phase 1 study with CYT-0851 in combination with capecitabine or gemcitabine in a poster titled "Phase 1 Results of CYT-0851, a Monocarboxylate Transporter (MCT) Inhibitor, in Combination with Capecitabine or Gemcitabine in Advanced Solid Tumors" (Abstract: 3099, Poster: 297) at the 2023 American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) annual meeting in Chicago, Illinois (Press release, Cyteir Therapeutics, JUN 3, 2023, View Source [SID1234632467]).

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"We are encouraged by the preliminary data from the Phase 1 dose escalation study with CYT-0851 in combination with capecitabine and gemcitabine and are pleased that the safety profile of CYT-0851 continues to be generally tolerable even when combined with these standard chemotherapy agents," said Markus Renschler, MD, President and Chief Executive Officer of Cyteir. "The Cyteir team is diligently executing on the clinical development of CYT-0851 as a potential combination therapy, and we look forward to sharing preliminary data for all patients in these cohorts mid-year."

Phase 1 Study Objectives

The primary objective of the ongoing Phase 1 study is to determine the recommended Phase 2 dose and maximum tolerated dose of CYT-0851 in combination with capecitabine or gemcitabine. Key secondary objectives include evaluation of safety and tolerability, determination of the pharmacokinetic parameters, optimal dosing regimen for each combination and characterization of preliminary anti-tumor activity of the combinations.

Phase 1 Study Preliminary Findings

The data presented in the poster are the first report of preliminary results of an ongoing study.

As of the May 1, 2023 data cutoff, 22 patients were enrolled in the capecitabine cohort across four dose-escalation cohorts from 100 mg to 400 mg once daily dose and 13 patients were enrolled in the gemcitabine cohort across three dose-escalation cohorts from 100 mg to 300 mg once daily dose. Fourteen patients in the capecitabine arm were response evaluable and eight patients in the gemcitabine arm were response evaluable.

The recommended Phase 2 dose in the capecitabine combination is 400 mg once a day with no dose limiting toxicities observed. The maximum tolerated dose in the combination of CYT-0851 with

capecitabine was not identified. The dose escalation of CYT-0851 in combination with gemcitabine is ongoing and the study has cleared the 200 mg dose.

Combination of CYT-0851 with capecitabine

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Seven ovarian cancer patients and seven pancreatic cancer patients were response evaluable with RECIST measurements available.
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There was one partial response in an ovarian cancer patient with treatment ongoing in cycle 12 and nine patients had stable disease (five pancreatic cancer patients and four ovarian cancer patients).
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The overall disease control rate in the capecitabine combination was 71.4%.
Combination of CYT-0851 with gemcitabine

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Five sarcoma patients, two pancreatic cancer patients and one ovarian cancer patient were response evaluable.
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There was one confirmed partial response in a sarcoma patient at month two and six patients with stable disease (three sarcoma patients, two pancreatic patients and one ovarian cancer patient).
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The overall disease control rate was 87.5%.
Safety:

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To date, CYT-0851 has exhibited a generally well tolerated safety profile without unanticipated toxicities observed at clinically active doses, and without exacerbation of the expected toxicity from the chemotherapy combination partners.
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In the capecitabine cohort, 45.5% of patients reported adverse events with 9.1% being grade 3/4. The most common treatment-related adverse events were fatigue (27.3%), decreased appetite (13.6%) and nausea (13.6%).
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In the gemcitabine cohort, 69.2% of patients reported adverse events with 46.2% being grade 3/4. The most common treatment-related adverse events were fatigue (38.5%), anemia (23.1%) and neutropenia (23.1%).
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No dose-limiting toxicities were observed in any patients treated with the combination of CYT-0851 and capecitabine.
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In the CYT-0851 plus gemcitabine combination cohorts, one patient at the 300 mg level had dose-limiting hyperglycemia with starvation ketoacidosis that resolved upon treatment interruption and has not recurred upon rechallenge at a lower dose.
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No treatment related deaths have been reported, and no patients experienced a treatment related adverse event that led to discontinuation of CYT-0851.