Safety, Tolerability, and Pharmacokinetics of TAK-931, a Cell Division Cycle 7 Inhibitor, in Patients with Advanced Solid Tumors: A Phase I First-in-Human Study

Purpose: We conducted a first-in-human, dose-escalation study, to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics, and activity of TAK-931, a cell division cycle 7 inhibitor, in Japanese patients with advanced solid tumors. Experimental Design: Patients ages ≥20 years received oral TAK-931: once daily for 14 days in 21-day cycles (schedule A; from 30 mg); once daily or twice daily for 7 days on, 7 days off in 28-day cycles (schedule B; from 60 mg); continuous once daily (schedule D; from 20 mg); or once daily for 2 days on, 5 days off (schedule E; from 100 mg) in 21-day cycles. Results: Of the 80 patients enrolled, all had prior systemic treatment and 86% had stage IV disease. In schedule A, 2 patients experienced dose-limiting toxicities (DLTs) of grade 4 neutropenia and the maximum tolerated dose (MTD) was 50 mg. In schedule B, 4 patients experienced DLTs of grade 3 febrile neutropenia (n = 3) or grade 4 neutropenia (n = 1); the MTD was 100 mg. Schedules D and E were discontinued before MTD determination. The most common adverse events were nausea (60%) and neutropenia (56%). Time to maximum plasma concentration of TAK-931 was approximately 1–4 hours postdose; systemic exposure was approximately dose proportional. Posttreatment pharmacodynamic effects correlating to drug exposure were observed. Overall, 5 patients achieved a partial response. Conclusions: TAK-931 was tolerable with a manageable safety profile. TAK-931 50 mg once daily days 1–14 in 21-day cycles was selected as a recommended phase II dose and achieved proof of mechanism. Trial registration ID: NCT02699749 Significance: This was the first-in-human study of the CDC7 inhibitor, TAK-931, in patients with solid tumors. TAK-931 was generally tolerable with a manageable safety profile. The recommend phase II dose was determined to be TAK-931 50 mg administered once daily on days 1–14 of each 21-day cycle. A phase II study is ongoing to confirm the safety, tolerability, and antitumor activity of TAK-931 in patients with metastatic solid tumors.

TAK-931 (simurosertib) is an oral, highly potent, selective kinase inhibitor of CDC7 with demonstrated replication, stress-mediated antiproliferative activity across various cancer cell lines (15). In murine xenograft models of human colorectal, lung, ovarian, and pancreatic cancer, TAK-931 treatment causes significant and irreversible tumor growth inhibition, with favorable pharmacokinetic and pharmacodynamic profiles (15). In Japan, we conducted a first-in-human study of TAK-931 to evaluate the safety, tolerability, maximum tolerated dose (MTD), and recommended phase II dose (RP2D) in adults with advanced solid tumors.

Patients
Patients aged ≥20 years with histologically confirmed, advanced solid tumors (except primary brain tumors), an Eastern Cooperative Oncology Group performance status of 0/1, and for whom no effective standard therapy was available were eligible. Patients with seizures requiring antiepileptic treatment, symptomatic and/or progressive central nervous system metastases, blood pressure conditions, a history of ischemic myocardial, ischemic cerebrovascular, or thromboembolic events within 3 months before the first dose of TAK-931, or a history of orthostatic hypotension or syncope requiring medical intervention, or postural tachycardia syndrome were excluded. See Supplementary Materials and Methods for full eligibility criteria.

Study Design
This was a phase I, open-label, dose-escalation study of single-agent TAK-931.
Dose escalation of TAK-931 was cohort based with an adaptive design using Bayesian logistic regression modeling (BLRM) with pharmacokinetic guidance. BLRM also guided MTD estimation from the second dose. Patients were enrolled in one of four dosing schedules (A, B, D, or E; Supplementary Fig. S1) to receive TAK-931. Two additional schedules were planned (C and F) but no patients were enrolled. Schedule A included an initial accelerated escalation phase. TAK-931 was administered once daily for 14 days in 21-day cycles starting at 30 mg, which doubled until a cycle 1 dose-limiting toxicity (DLT) was observed, when 2 patients experienced grade ≥2 treatment-related toxicity, or when maximum geometric mean plasma concentration (C max ) for the cohort reached or exceeded 800 ng/mL [threshold for off-target adverse effects (hypotension) in animal toxicology studies]; then dose escalation transitioned to modified Fibonacci escalation steps. In schedule B (based on experience with schedule A), patients received TAK-931 once daily or twice daily for 7 days on, 7 days off in a 28-day cycle starting at 60 mg. In schedule D, patients received TAK-931 once daily starting at 20 mg in 21-day cycles; BLRM was not applied but further adjustments were dependent on observed safety, pharmacokinetics, and pharmacodynamics. In schedule E, patients received TAK-931 once daily for 2 days on, 5 days off starting at 100 mg in 21-day cycles. A safety expansion was permitted once MTD had been determined. Prophylactic growth factors were permitted in all schedules to manage severe and/or febrile neutropenia. TAK-931 treatment continued until unacceptable toxicity, disease progression, or patient withdrawal.
The primary objectives were to evaluate safety, tolerability, and to identify the MTD of TAK-931. Secondary objectives were to characterize the pharmacokinetics of TAK-931, assess pharmacodynamic effects of TAK-931 by measuring basal and postdose levels of skin phosphorylated MCM2 (pMCM2; a CDC7 substrate), and assess preliminary clinical activity of TAK-931. An exploratory objective was to assess the pharmacodynamic effect of TAK-931 in fresh tumor biopsies after multiple doses of TAK-931 that were considered to have biological effect.
This study was conducted according to the protocol, the ethical principles that have their origin in the Declaration of Helsinki, the International Council for Harmonization Harmonized Tripartite Guideline for Good Clinical Practice, and all applicable regulations. The study protocol was reviewed and approved by the local or central Institutional Review Boards at all study sites. Patients provided written informed consent.

Assessments
DLTs included: cycle 1 grade ≥3 hematologic and non-hematologic events or grade 2 non-hematologic events considered by the investigator to be TAK-931-related, grade 2 ejection fraction decrease, >2 weeks delay in initiating cycle 2 (1 week for schedules D and E), and >50% TAK-931 dose reduction in cycle 1 due to treatment-related adverse events (AEs; see Supplementary Materials and Methods for full DLT criteria). Toxicity was evaluated by NCI Common Terminology Criteria for Adverse Events (version 4.03).
Tumor response was measured using the RECIST (version 1.1) (16). Serial blood samples for pharmacokinetic analysis were collected during cycle 1 on days 1 and 7 (schedule B), 1 and 8 (schedules A and D), or 1 and 9 (schedule E). Pharmacokinetic parameters were estimated from concentration-time profiles using noncompartmental methods with WinNonlin R Phoenix TM version 8.1 (Certara, Princeton, NJ). pMCM2 was detected semiquantitatively by IHC of histologic sections of formalin-fixed, paraffin-embedded skin and tumor biopsies using anti-pMCM2 (3378-1, Epitomics Inc.; ref. 15). Quantitative image analysis determined pMCM2 levels as "histologic score nuclei (H-score)." Skin punch biopsies (2-4 mm) were obtained during screening or predose on cycle 1, day 1 and for patients in schedules A, B, and D, postdose on any drug dosing day after 3 consecutive dosing days in cycle 1. A postdose skin biopsy was obtained on day 9 in schedule E. Fresh tumor biopsy pairs were collected predose and postdose on any dosing day after the completion of 3 consecutive dosing days in cycle 1 from patients who received doses considered to have biological effect.

Statistical Analysis
The safety population included patients who received ≥1 dose of TAK-931. The pharmacodynamic-evaluable population comprised patients from the safety population with a baseline and ≥1 additional postbaseline biopsy sample that was suitable for pMCM2 analysis. The pharmacokinetic-evaluable population included patients with sufficient dosing and TAK-931 concentration-time data to estimate pharmacokinetic parameters. The response-evaluable population included patients in the safety population with measurable disease at baseline and ≥1 postbaseline response assessment.

Data Availability Statement
The datasets, including the redacted study protocol, redacted statistical analysis plan, and individual participants' data supporting the results reported in

AACRJournals.org
Cancer Res Commun; 2(11) November 2022  this article, will be made available within 3 months from initial request, to researchers who provide a methodologically sound proposal. The data will be provided after its deidentification, in compliance with applicable privacy laws, data protection, and requirements for consent and anonymization. Patient demographics and baseline characteristics are shown in Table 1. Median age was 59 years overall. Common diagnoses included esophageal squamous cell cancer (16%) and pancreatic cancer (13%). Patients had advanced disease (86% stage IV) and were heavily pretreated. At data cutoff (April 6, 2020), all patients had discontinued the study, mostly due to progressive disease (90%; Supplementary Fig. S2).

DLTs and MTD
In schedule A, 2 of 3 patients receiving TAK-931 60 mg experienced DLTs of grade 4 neutropenia lasting >3 days, per the protocol definition of DLT at the time; the MTD was determined as 50 mg based on DLT incidence, relative dose intensity, pharmacokinetic, and AE profiles at this dose. In schedule B, DLTs of grade 3 febrile neutropenia were experienced by 2 of 9 patients receiving TAK-931 80 mg and one of six patients receiving TAK-931 120 mg. One of 6 patients receiving TAK-931 100 mg experienced a DLT of grade 4 neutropenia lasting >7 days (following a protocol amendment, the criteria for grade 4 neutropenia being considered a DLT was changed from lasting >3 days to lasting >7 days). The MTD for this schedule was determined as 100 mg based on DLTs, a low relative dose intensity, and high frequency of AEs at 120 mg. Although

Safety and Tolerability
Across all schedules, patients received a median of 3.0 (range,

Pharmacodynamics
Pharmacodynamic response to TAK-931 was assessed in skin biopsies from 47 patients predose and on cycle 1, day 8 postdose (Table 4). TAK-931 suppressed skin pMCM2 levels from 34.1% to 90.9% postdose. Individual H-scores from baseline and postdose as well as best overall response of 9 patients with evaluable skin biopsy data in schedule A are shown in Fig. 2A. Tumor type and best response to TAK-931 for these patients are also shown in Supplementary Table S1. Suppression of skin pMCM2 by TAK-931 appeared to be dose dependent and was positively correlated with TAK-931 exposure (AUC 0-24; P β = 0 = 0.000052, R 2 = 0.9158; Fig. 2B). TAK-931 also suppressed pMCM2 in tumor tissue biopsies as shown by IHC staining for pMCM2 in an individual patient from schedule D dosed at 30 mg (Fig. 2C).

Antitumor Activity
Seventy-five patients were response evaluable (Supplementary  Supplementary Fig. S4A and computerized tomography scans from 2 responding patients are shown in Supplementary   Fig. S4B and S4C. In schedule B, ORR was 9%: 1 patient with esophageal cancer receiving TAK-931 100 mg achieved a PR maintained for 4.2 months and 1 patient with anal cancer receiving TAK-931 120 mg achieved a PR but discontinued at the same visit on the advice of the investigator due to worsening of symptoms (hoarseness and dysphagia). Overall, 28 patients achieved a best response of SD. One patient with cervical cancer in schedule D (40 mg) achieved SD lasting for 15.24 months. Two patients in schedule A (50 mg) with cervical cancer and thymic cancer achieved SD for 11.33 and 10.45 months, respectively. Overall, median progression-free survival was 2.2 months (95% confidence interval, 1.94-3.06).

Discussion
This was the first-in-human study of a CDC7 inhibitor in patients with solid tumors. The MTD of TAK-931 was 50 mg once daily on days 1-14 of a 21-day treatment cycle (schedule A), or 100 mg on days 1-7 and days 15-21 of a 28-day cycle (schedule B) based on DLTs, relative dose intensity, and AE profiles. Dose escalation of continuous daily dosing and twice-weekly dosing schedules were discontinued because of changes in the sponsor's development strategy and not  analyses would need to investigate rational combination approaches (20). Interestingly, this study also excluded patients with significant baseline hypotension, and reported rates of drug-related orthostatic hypotension of 50%, suggesting that hypotension may be a class effect of CDC7 inhibition (20). In our study, cardiovascular (hypotension) and renal toxicity were anticipated on the basis of preclinical animal studies (Takeda, data on file); however, the eligibility criteria excluded patients with a history of cardiovascular and blood pressure conditions to mitigate potential toxicity, and clinical and urine chemistry were used to monitor potential renal effects. Cardiovascular events were all grade 1/2 and nonserious and no clinically relevant decrease in CLr was observed.
TAK-931 has potential applications in combination with other DDR inhibitors, including poly ADP ribose polymerase (PARP) inhibitors. PARP inhibitors are used to treat malignancies that exhibit the "BRCAness" phenotype, which is the loss of function of the homologous recombination DDR pathway (21). Impairment of two DDR mechanisms can prevent one pathway compensating for the loss of the other (22). Preclinical findings suggest that TAK-931 could induce "BRCAness" in cancer cells, enhancing antiproliferative activity of PARP inhibitors (23). Indeed, TAK-931 suppressed DNA repair activity and enhanced the biological activity of PARP inhibitors, topoisomerase inhibitors, and platinum compounds in human xenograft models (23,24). While there is potential for overlapping hematologic toxicity, clinical investigation of these combinations is warranted.

Conclusions
TAK-931 was tolerable, with a manageable safety profile in patients with advanced solid tumors. On the basis of these results, TAK-931 50 mg once daily on days 1-14 of a 21-day cycle is being investigated in a phase II study in patients with metastatic pancreatic cancer, colorectal cancer, esophageal squamous cell cancer, or squamous non-small cell lung cancer (NCT03261947). A tablet formulation of TAK-931 is in development to address scalability in larger trials (NCT03708211).

Authors' Disclosures
Y. Kuboki reports grants and personal fees from Takeda during the conduct of the study; grants and personal fees from Taiho, Lilly, Boehringer Ingelheim, Bristol-Myers-Squibb; grants from Astelas, Daiichi-Sankyo, As-traZeneca, Chugai, Genmab, GlaxoSmithkline, Incyte, Abbie; grants, personal fees, and non-financial support from Amgen outside the submitted work. T. Shimizu reports grants and personal fees from Takeda during the conduct of the study; grants from AbbVie, Eli Lilly, LOXO Oncology, Novartis,