TAS-115 mini-tablets

Round, film-coated, mini-tablets containing 50 mg TAS-115 (drug substance) as free base. Each tablet contains the following inactive ingredients: hydroxypropyl-β-cyclodextrin, light anhydrous silicic acid, hydroxypropyl cellulose, magnesium stearate, hypromellose, macrogol 6000, titanium oxide, and yellow ferric oxide.

Pioglitazone

ACTOS® Tablets 15 was used as pioglitazone.

Losartan

Losartan potassium tablets 25 mg [“TEVA”] was used as losartan.

Midazolam

BUCCOLAM® oromucosal solution 2.5 mg was used as midazolam. We prepared an oral solution by diluting BUCCOLAM oromucosal solution with 5% dextrose injection solution. First, we combined the entire content of the BUCCOLAM oromucosal solution with 20 mL of 5% dextrose injection solution in a dosing bottle, ensuring the mixture did not stick to the lid. To prevent buccal absorption and ensure that BUCCOLAM oromucosal solution was primarily absorbed through the gastrointestinal tract, patients were then instructed to swallow the solution immediately. Next, we added another 20 mL of 5% dextrose injection solution to the same bottle, mixed again, and the patient swallowed this solution as well to ensure complete transfer to the stomach.

Patients: major eligibility criteria

Eligible patients were those with solid tumors aged 20 years or older (or with malignant bone tumors aged 15 years or older) who were refractory or intolerant to standard treatments, or for whom no appropriate treatments were available. All patients were required to provide informed consent. Detailed inclusion and exclusion criteria are described in the Supplementary material section.

Sample size

The target sample size for this study was 18 patients. Assuming that the intra-individual coefficient of variation of the pharmacokinetic (PK) parameters of the cytochrome P450 (CYP) substrates was 30%, when the true ratios of the geometric mean of the PK parameters of a single CYP substrate before and after coadministration of TAS-115 were 1.25 and 1.5, the probability that the lower limit of the 90% confidence interval (CI) of the ratio of the geometric mean obtained from 16 patients exceeds 1 was 66% and 98%, respectively. Although no hypothesis testing was specified in determining the primary objective of this study, it was considered reasonable to set a sample size of approximately 16 patients, in order to preserve an acceptable threshold for detecting an effect. We decided to enroll 18 patients, to allow for possible dropouts.

Rationale for dosing plan of marker substrates in this study

The Inje cocktail, which contains losartan and midazolam, has been established as a substrate cocktail [21]. However, because there have been no studies using cocktail substrates containing pioglitazone, we planned to administer pioglitazone on a separate day. To maximize the time-dependent inhibitory effect of TAS-115 on CYP3A, we administered midazolam, a CYP3A substrate, on Day 5 of once-daily TAS-115 administration. Therefore, we evaluated the interaction of TAS-115 with pioglitazone on Day 4 of TAS-115 administration, and with losartan and midazolam on Day 5.

Study design

This multicenter, open-label, single-arm study evaluated the effect of multiple oral doses of TAS-115 on the PKs of single oral doses of pioglitazone (CYP2C8 substrate), losartan (CYP2C9 substrate), and midazolam (CYP3A substrate) in patients with solid tumors. The study was conducted in Japan. The study comprised two phases: a DDI evaluation period and a continuous administration period. During the DDI evaluation period, patients received a single oral dose of pioglitazone (CYP2C8 substrate) followed by the cocktail dosing of losartan (CYP2C9 substrate) and midazolam (CYP3A4 substrate) both before and during multiple oral doses of TAS-115 to evaluate the impact on individual drug PKs with and without TAS-115. Patients meeting the continuous administration period criteria proceeded to the continuous administration period, where TAS-115 was administered in a 21-day cycle (5 days on, 2 days off) until treatment discontinuation criteria were met. The study design is shown in Fig. 1.

Fig. 1

An overview of the dosing schedule. Day 1 was defined as the first day of TAS-115 administration. F/U follow-up. Cy Cycle: a 21-day cycle (5 days on, 2 days off)

DDI Evaluation Period: Following screening, an eligible patient was hospitalized the day before the first dose of pioglitazone was administered. Day 1 was defined as the first day of TAS-115 administration. The patient received pioglitazone 15 mg on Day − 3 and Day 4 (30 min after TAS-115 dosing) and losartan 25 mg and midazolam 2.5 mg on Day − 2 and Day 5 (30 min after TAS-115 dosing) to evaluate individual drug PKs. The patient received multiple doses of TAS-115 at 250 mg once daily from Day 1 to Day 5, which was the planned maximum clinical daily dose. All treatments were performed in the fasted state. The patient was to be discharged when no clinically significant findings were found by the specified tests on Day 8 (acceptable time window, − 2 days). Concomitant use of medications or foods that may affect the evaluation of DDI (e.g., agents known to inhibit or induce CYP2C8, CYP2C9, or CYP3A) was prohibited during the DDI evaluation period.

Continuous administration period: If a patient wished to continue treatment with TAS-115 and met the continuous administration period criteria, he or she started to receive TAS-115 within 14 days after the tests at the end of treatment in the DDI evaluation period. Patients received 250 mg TAS-115 in the fasted state for 5 consecutive days starting on Day 1 of each 21-day cycle, followed by 2 days off, in repeated cycles. Patients continued receiving TAS-115 until the criteria for discontinuation of study treatment were met.

OutcomesPrimary endpoint

PK parameters of pioglitazone, losartan, and midazolam (maximum plasma concentration [Cmax], area under the plasma concentration-time curve up to the last observable concentration [AUClast], area under the plasma concentration-time curve from time 0 to infinity [AUCinf]).

Secondary endpoints

PK parameters of pioglitazone, losartan, and midazolam (time to maximum plasma concentration [Tmax], terminal elimination rate constant [λz], terminal elimination half-life [T1/2], mean residence time [MRT], oral clearance [CL/F], apparent volume of distribution [Vz/F]) and 1’-hydroxymidazolam (Cmax, AUClast, AUCinf, Tmax, λz, T1/2, metabolite-to-parent molar ratio for maximum plasma concentration [MRCmax], metabolite-to-parent molar ratio for area under the plasma concentration-time curve up to the last observable concentration [MRAUClast], metabolite-to-parent molar ratio for area under the plasma concentration-time curve from time 0 to infinity [MRAUCinf]).

PK parameters of TAS-115.

Incidence and severity of adverse events (AEs), changes in vital signs and laboratory values, electrocardiogram (ECG) changes.

Overall response rate (ORR), disease control rate (DCR), and progression-free survival (PFS) evaluated based on the assessment of the investigator according to Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1.

Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 was used to grade the severity of AEs.

Bioanalytical methods

Blood samples were collected for PK analysis from Day − 3 to Day 2 and from Day 4 to Day 6. Detailed sampling points are shown in Supplementary Table S1. The plasma concentrations of pioglitazone, losartan, midazolam, 1’-hydroxymidazolam, and TAS-115 were determined using validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. Stable isotope-labeled internal standards of each analyte were used. Samples extracted by solid-phase extraction (for pioglitazone, losartan, midazolam, and 1’-hydroxymidazolam) and deproteinization (for TAS-115) were injected onto C18 reverse-phase columns, before detection by mass spectrometers (API 400 or Triple Quad 5500, AB SCIEX). The calibration ranges were 5–2000 ng/mL for pioglitazone, 1–1000 ng/mL for losartan, 0.02–50 ng/mL for midazolam and 1’-hydroxymidazolam, and 10–10,000 ng/mL for TAS-115. Within- and between-rum precision were ≤ 6.4% and ≤ 6.9%, respectively, for pioglitazone, ≤ 11.7% and ≤ 10.0%, respectively, for losartan, ≤ 4.3% and ≤ 6.0%, respectively, for midazolam, ≤ 5.2% and ≤ 5.5%, respectively, for 1’-hydroxymidazolam, and ≤ 3.9% and ≤ 3.6%, respectively, for TAS-115. Within- and between-run accuracy ranged from − 10.8% to 4.8% and from − 3.2% to 0.8%, respectively, for pioglitazone, from − 12.3% to 7.6% and from − 9.3% to 3.8%, respectively, for losartan, from − 6.5% to 4.0% and − 0.2% to 4.0%, respectively, for midazolam, from 3.8% to 6.5% and from 0% to 5.3%, respectively, for 1’-hydroxymidazolam, and from − 8.2% to 0.9% and − 4.3% to −0.5%, respectively, for TAS-115.

Statistical methods

PK parameters for pioglitazone, losartan, midazolam, 1’-hydroxymidazolam, and TAS-115 were estimated using non-compartmental methods. Log-transformed PK parameters (Cmax, AUClast, AUCinf) were analyzed using a linear mixed-effects model with treatment as a fixed effect and patient as a random effect using Phoenix® WinNonlin® software version 8.1 (Certara, LP, Princeton, NJ, USA). Geometric least squares mean ratios and 90% CI values were calculated. The linear mixed effect model analyses were performed using SAS software version 9.4 and SAS/STAT software version 15.1 or a later version.

Efficacy evaluation methods

The efficacy values were evaluated using the following definitions. The ORR, DCR, and PFS were evaluated based on the RECIST version 1.1. ORR was defined as the percentage of patients with a best overall response of complete response (CR) or partial response (PR). DCR was defined as the percentage of patients with a best overall response of CR, PR, or stable disease (SD). The PFS was defined as the period from the date of enrollment to the date of confirmation of progressive disease (PD) or the date of death from any cause, whichever came earlier. For patients receiving any subsequent treatment before the diagnosis of PD after the completion of treatment with TAS-115, PFS data was to be censored on the date of the last imaging scan performed before the start of the subsequent treatment. For patients who were alive without diagnosis of PD at the time of analysis, PFS data were censored on the date of the last imaging scan. Overall survival (OS) was evaluated in patients with osteosarcoma. OS was defined as the period from the date of enrollment to the date of death due to any cause. If the patient was alive at the time of analysis, the censoring date was the date of the last follow-up assessment, the date of the last survival follow-up, or the date of any other recorded test or observation, whichever occurred the last.

Safety evaluation methods

All AEs occurring between the first dose of pioglitazone and the end of the safety follow-up period (28 days [acceptable up to + 7 days] after the last dose of TAS-115, pioglitazone, losartan, or midazolam) or the date when any of the criteria for discontinuation of the safety follow-up period are met, whichever comes earlier, were collected. AEs considered by the investigator to be related to TAS-115, pioglitazone, losartan, or midazolam were also collected even if they occurred after the safety follow-up period. The CTCAE version 5.0 was used to grade the severity of AEs.

Compliance with ethical standards

This study was conducted in accordance with the clinical protocol and consensus ethical principles derived from international guidelines including the Good Clinical Practice (GCP) Ordinance, the ethical principles that have their origin in the Declaration of Helsinki, and other applicable laws and regulations.

Consent to participate

The investigator or his/her representative explained the nature of the study to the patient and answered all questions regarding the study. Patients were informed that their participation was voluntary. Patients were required to sign a statement of informed consent that met the requirements of the local regulations and the Institutional Review Board (IRB) or study site. Investigative sites were instructed to obtain written informed consent prior to any study-related assessments or procedures in the study and document the date when the written consent was obtained. The investigator obtaining the informed consent was also instructed to sign the Informed Consent Form (ICF). If the clinical research coordinator provided a supplementary explanation, he or she was to sign the ICF. If there were any amendments during their participation in the study, patients were re-consented to the most current version of the ICF(s). A copy of the ICF(s) was provided to the patient.

Consent to publish

All patients agreed to the secondary use of clinical trial results in academic conferences and papers through the ICF.