Phase I and pharmacokinetic study of the vascular‐disrupting agent CKD‐516 (NOV120401) in patients with refractory solid tumors

Abstract We report a phase I pharmacological study of an oral formulation of CKD‐516, a vascular‐disrupting agent, in patients with refractory solid tumors. Twenty‐seven patients (16 in the dose‐escalation cohort and 11 in the expansion cohort) received a single daily dose (5‐25 mg) of CKD‐516 five days per week. Nausea (67%) and diarrhea (63%) were the most common treatment‐related adverse events. The recommended phase II dose of oral CKD‐516 was 20 mg/d (15 mg/d with a body surface area (BSA) <1.65 m2). Notably, S‐516 half‐lives in patients receiving 15‐20 mg CKD‐516/d significantly differed between patients with and without splenomegaly that is suggestive of portal hypertension associated with liver cirrhosis (6.1 vs 4.6 hours, respectively). Of 11 patients without splenomegaly who completed at least one cycle of a daily CKD‐516 dose of either 15 or 20 mg, only one patient (9.1%) suffered from any dose‐limiting toxicity. We conclude that a daily oral dose of 15 or 20 mg CKD‐516 five days per week could be tolerable in patients without liver cirrhosis.

Chong Kun Dang (Seoul, Korea), is a VDA prodrug that is rapidly converted into the active moiety, S-516. 7-10 S-516 possesses strong antitumor activity and can increase the antitumor activities of various chemotherapeutic and/or immunotherapeutic regimens. [7][8][9][10] CKD-516 was shown to exhibit a manageable safety profile in patients with solid tumors in an intravenous injection clinical study (NCT01028859). 11 Using doses up to 9 mg/m 2 (days 1 and 8, every 3 weeks), intravenous CKD-516 resulted in no dose-limiting toxicities (DLT); however, a weekly intravenous infusion of 12 mg/m 2 CKD-516 led to two cases of grade 3 hypertension, considered a DLT. 11 A subsequent study (NCT01560325) demonstrated that more frequent dosing of CKD-516 was not associated with increases in toxicity. An oral formulation of CKD-516 was developed to improve its efficacy and patient compliance. Here, we report a phase I pharmacological study to determine the optimal dosing regimen for oral CKD-516 in patients with refractory solid tumors.

| MATERIAL S AND ME THODS
This was a single-institution, phase I study conducted at the National Cancer Center Korea (ClinicalTrials.gov identifier, NCT02300467). All patients provided informed consent for the study protocol, which was approved by the National Cancer Center Institutional Review Board (NCCIRB 2014-0174). Eligibility criteria included age greater than or equal to 19 years; Eastern Cooperative Oncology Group (ECOG) performance score less than or equal to 2; and adequate bone marrow, renal, and hepatic function [absolute neutrophil count ≥ 1500/mm 3 , platelet count ≥ 100 000/mm 3 , hemoglobin ≥ 9.0 g/dL, serum creatinine level ≤ 1.5 g/dL, or a calculated creatinine clearance ≥ 50 mL/ min, aspartate transaminase (AST) and alanine transaminase (ALT) ≤3 × the upper limit of normal (ULN) or ≤ 5× the ULN in cases of liver involvement, bilirubin ≤ 1.5 × the ULN, and prothrombin time and activated partial thromboplastin time ≤ 1.5 × the ULN]. Patients were required to have histologically or cytologically confirmed cancers that were refractory to at least 1 therapeutic regimen for metastatic disease. In cases of hepatocellular carcinoma (HCC), histological confirmation was not required if α-fetoprotein (AFP) levels were greater than or equal to 200 ng/mL, radiographic findings were consistent with HCC, and either HBsAg or anti-HCV was present. Previous chemotherapy was discontinued at least 2 weeks before study entry.

| Dosing schedule
After fasting or at least 2 hours after meal, oral CKD-516 tablets were administered to patients on days 1-5, 8-12, and 15-19 of a 3-week cycle (ie, 5 days on and 2 days off for better patient adherence). Treatment was planned for 12 cycles unless disease progression or unacceptable toxicity developed. The first dose for humans was 5 mg/d, which is one-tenth the human equivalent dose of the maximum tolerated dose in female rats (5 mg/kg/d), as calculated during a 2-week repeateddose toxicity test. A traditional 3 + 3 dose-escalation design was used for the dose-escalation phase. The expansion cohort was initially treated with a dose of 20 mg/d. Due to the DLT observed in the first patient, the study protocol was modified after 1 patient was treated so that the daily doses were 15 mg/d and 20 mg/d for a BSA less than and greater than or equal to 1.65 m 2 , respectively.

| Safety and efficacy assessments
Pretreatment evaluations consisted of a physical examination, an assessment of ECOG performance status and vital signs, 12-lead electrocardiography (ECG), a complete blood count (CBC), and blood chemistry levels. Positron emission tomography (PET) scans were performed to evaluate baseline disease status. Follow-up safety evaluations were performed at the beginning of each treatment cycle and at study termination, and included a physical examination, an assessment of vital signs and ECOG performance status, a CBC, and blood chemistry levels. Adverse events and evidence of toxicity were evaluated according to National Cancer Institute Common Criteria for Adverse Events (version 4.03). A DLT was defined as grade 4 neutropenia lasting more than 7 days, grade 3 or 4 neutropenic fever (>38.3°C), grade 4 thrombocytopenia, grade 3 thrombocytopenia with bleeding, or any treatment-related grade 3 or 4 nonhematologic toxicity. Grade 3 or 4 nausea, vomiting, diarrhea, and tumor pain lasting fewer than 3 days with symptomatic management were not considered DLTs.
The following nonhematologic toxicities were considered DLTs if they persisted for longer than 7 days: grade 3 fatigue, hypertension (>140 mmHg/90 mmHg), and an elevation of AST or ALT > 5× the ULN. Treatment response was assessed by computed tomography (CT) 2 weeks before the first dose and every 8 weeks thereafter. CT was used to evaluate the presence of splenomegaly (defined as an enlargement of the spleen > 12 cm along the longest diameter), which is suggestive of portal hypertension associated with liver cirrhosis. Responses to therapy were evaluated primarily according to the RECIST guideline (v1.1). 12 PET scans were repeated 8 weeks after the first dose.

| Pharmacokinetics assessment
Sampling for the assessments of pharmacokinetics parameters was The estimates of the regression parameter (β 1 ) and its 2-sided 95% confidence intervals (CI) were derived from the equations.
Adjusted R 2 was calculated between log-transformed CKD-516 dose and the log-transformed pharmacokinetic parameters.

| Enrollment
Twenty-seven patients (16 in the dose-escalation cohort and 11 in the expansion cohort) received at least one dose (5-25 mg/d) of the study drug (Table 1). The median age of the patients was 55.7 years. Treatment was discontinued due to disease progression and toxicity in 19 (70.4%) and 7 (25.9%) patients, respectively, whereas one patient withdrew consent before the completion of the study. The average duration of drug administration was 31.9 days, and the average treatment cycle duration was 2.4 cycles. The average daily dose was 16.1 mg CKD-516/d. Table 2 summarizes the treatment-related adverse events that were observed in at least 10% of patients. Nausea/vomiting and diarrhea were the most common treatment-related adverse events.

| Safety profiles in the dose-escalation cohort
Sixteen patients were enrolled in the dose-escalation cohort. At dose level 2 (10 mg/d), 1 patient was removed from the trial during the DLT evaluation period due to early disease progression. Hence, DLT was only evaluated in 15 patients (Table 3)

| Safety profiles in the expansion cohort
Given that CKD-516 is a VDA, we augmented the expansion cohort with patients who had hypervascular tumors, such as HCC (n = 5) and renal cell carcinomas (n = 3). Patients in the expansion cohort were initially treated with 20 mg CKD-516/d, which did not cause any DLTs during the dose-escalation phase. The first patient with HCC (BSA, 1.34 m 2 ) treated with this dose, however, developed a DLT (jaundice). As a patient with HCC (BSA, 1.73 m 2 ) did not develop DLT after the same dose (20mg) in the dose level 3, the study protocol was then modified so that the daily doses were set at 15 mg/d and 20 mg/d for a BSA less than and greater than or equal to 1.65 m 2 , respectively. This modified BSA-based dosing regimen was used for the next 10 patients enrolled in the expansion cohort. Of these patients, 7 were evaluated for DLTs, 1 patient withdrew from the trial, and 2 patients were removed from the trial due to early disease progression. Of the 7 evaluated patients, 3 developed a DLT (nausea, thrombocytopenia, and sepsis). Notably, 2 of these 3 patients had HCC accompanied by splenomegaly. Among the dose-escalation and expansion cohorts, 11 patients without any evidence of splenomegaly completed at least 1 cycle of a daily CKD-516 dose of either 15 or 20 mg, depending on BSA status.

TA B L E 1 Patient characteristics
Of these 11 patients, only 1 patient (9.1%) suffered from any DLT.

| Efficacy
Twenty-two patients were evaluated for drug efficacy (3, 4, 6, and 9 patients for dose levels 1, 2, and 3, and the expansion cohort, respectively  Notably, the T 1/2 of S-516 was significantly prolonged in cases showing radiographic evidence of splenomegaly. As shown in

| Pharmacokinetics assessment
TA B L E 2 Treatment-related adverse events with a total incidence > 10%

| D ISCUSS I ON
An oral formulation of CKD-516 was developed to improve the drug's anticancer activity and patient compliance. In this study, other VDAs. [4][5][6]11,14 One pharmacological benefit of CKD-516 is its rapid absorption.
We observed that the T max of S-516 was relatively short (0.5-1 hours), which indicates that oral CKD-516 is rapidly absorbed and quickly   F I G U R E 3 T 1/2 of S-516 in patients receiving 15-20 mg CKD-516/d with or without radiographic evidence of splenomegaly (P = .0016, t test). All patients who received at least 1 CKD-516 dose were analyzed, including those who could not complete the first cycle of CKD-516 administration due to disease progression. Box plots display 5%, 25%, median, 75%, and 95% T 1/2 values, with outliers shown as dots