Combination of GT90001 and nivolumab in patients with advanced hepatocellular carcinoma: a multicenter, single-arm, phase 1b/2 study.

BACKGROUND: GT90001 (also known as PF-03446962) is an anti-ALK-1 monoclonal antibody and has shown activity in hepatocellular carcinoma (HCC). This phase 1b/2 study was designed to determine the recommended phase 2 dose (RP2D) of GT90001 plus nivolumab, and assess the safety and anti-tumor activity in patients with advanced HCC. METHODS: Patients with advanced HCC were recruited from 3 centers. Eligible patients in the dose de-escalation stage received the GT90001 on day 1 of a 14-day cycle in a rolling-six design with a fixed dose of nivolumab (3.0 mg/kg). Patients in dose-expansion stage received the RP2D of GT90001 plus nivolumab. Primary endpoint was safety. Key secondary endpoint was objective response rate (ORR) as per RECIST 1.1. RESULTS: Between July 9, 2019, and August 8, 2022, 20 patients were treated (6 in phase 1b; 14 in phase 2) and evaluable for analysis. In phase 1b, no dose-limiting toxicities were observed, and GT90001 7.0 mg/kg was confirmed as the RP2D. Common grade 3/4 adverse events (AEs) were platelet count decreased (15%). No deaths due to AEs were reported. Confirmed ORR and disease control rate were 30% (95% CI, 14.6%-51.9%) and 40% (95% CI, 21.9%-61.3%), respectively. Median duration of response was not calculated (95% CI, 7.39 months to not calculated). Median progression-free survival (PFS) was 2.81 months (95% CI, 1.71-9.33), with 6-month and 12-month PFS rates of 35% and 25%, respectively. One patient with multiple intra- and extra-hepatic metastases was diagnosed with pseudo-progression upon GT90001 plus nivolumab exposure. CONCLUSIONS: GT90001 plus nivolumab has a manageable safety profile and promising anti-tumor activity in patients with advanced HCC. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov identifier NCT03893695.

Activity of preclinical and phase I clinical trial of a novel androgen receptor antagonist GT0918 in metastatic breast cancer.

PURPOSE: To evaluate GT0918, a 2nd-generation AR antagonist, for its AR down-regulation activity among breast cancer patients. METHODS: The effect of GT0918 on AR protein expression was evaluated in AR expression breast cancer cells and in breast cancer xenograft model. A 3 + 3 phase I dose-escalation study was launched in Peking University Cancer Hospital. The endpoints included dose finding, safety, pharmacokinetics, and antitumor activity. RESULTS: GT0918 was demonstrated to effectively suppress the expression of AR protein and the growth of AR-positive breast cancer tumors in mouse xenograft tumor models. All patients treated with GT0918 were at a QD dose-escalation of five dose levels from 100 to 500 mg. The most common treatment-related AEs of any grade were asthenia, anemia, decreased appetite, increased blood cholesterol, increased blood triglycerides, decreased white blood cell count, and increased low-density lipoprotein. Grade 3 AEs were fatigue (2 of 18, 11.1%), aspartate aminotransferase increase (1 of 18, 5.6%), alanine aminotransferase increase (1 of 18, 5.6%), and neutrophil count decrease (1 of 18, 5.6%). Clinical benefit rate (CBR) in 16 weeks was 23.1% (3/13). Among 7 AR-positive patients, 6 can evaluate efficacy, and 2 completed 23.5- and 25-cycle treatment, respectively (as of 2020/1/20). PK parameters showed a fast absorption profile of GT0918 in the single-dose study. GT0918 and its major metabolite reached steady-state serum concentration levels at day 21 after multiple dosing. CONCLUSION: GT0918 can effectively inhibit AR-positive breast cancer tumor growth. GT0918 was demonstrated well tolerated with a favorable PK profile. The suitable dose of GT0918 was 500 mg QD and may provide clinical benefits for AR-positive mBC.

A partially open conformation of an androgen receptor ligand-binding domain with drug-resistance mutations.

Mutations in the androgen receptor (AR) ligand-binding domain (LBD) can cause resistance to drugs used to treat prostate cancer. Commonly found mutations include L702H, W742C, H875Y, F877L and T878A, while the F877L mutation can convert second-generation antagonists such as enzalutamide and apalutamide into agonists. However, pruxelutamide, another second-generation AR antagonist, has no agonist activity with the F877L and F877L/T878A mutants and instead maintains its inhibitory activity against them. Here, it is shown that the quadruple mutation L702H/H875Y/F877L/T878A increases the soluble expression of AR LBD in complex with pruxelutamide in Escherichia coli. The crystal structure of the quadruple mutant in complex with the agonist dihydrotestosterone (DHT) reveals a partially open conformation of the AR LBD due to conformational changes in the loop connecting helices H11 and H12 (the H11-H12 loop) and Leu881. This partially open conformation creates a larger ligand-binding site for AR. Additional structural studies suggest that both the L702H and F877L mutations are important for conformational changes. This structural variability in the AR LBD could affect ligand binding as well as the resistance to antagonists.

Proxalutamide in patients with AR-positive metastatic breast cancer: Results from an open-label multicentre phase Ib study and biomarker analysis.

AIM: Proxalutamide is a novel second-generation non-steroidal androgen receptor (AR) antagonist. This study aimed to evaluate the preliminary efficacy and safety of proxalutamide in patients with AR-positive metastatic breast cancer (AR+ mBC). METHODS: In this open-label, dose-expansion, multicentre phase Ib trial, patients with AR+ mBC (immunohistochemistry [IHC] ≥1%) received proxalutamide orally once daily. Two proxalutamide dose cohorts (cohort A: 200 mg; cohort B: 300 mg) were sequentially investigated. Primary endpoints were disease control rate (DCR) at 8 and 16 weeks and recommended phase II dose (RP2D). RESULTS: Forty-five patients with three median lines (range, 1-13) prior systemic therapy were enrolled (cohort A, n = 30; cohort B, n = 15). Among 39 evaluable patients, DCR at 8 and 16 weeks was 25.6% (95% confidence interval [CI], 11.9-39.4%), with 26.9% in cohort A and 23.1% in cohort B. No patient achieved partial response or complete response. Proxalutamide 200 mg/day was determined as RP2D. The 6-month progression-free survival (PFS) rate was 19.6% (95% CI, 10.2-37.5%). In the triple-negative subgroup, DCR at 8 weeks was 38.5%, with median PFS of 9.1 months (95% CI, 7.8-NA) in those who achieved response at 8 weeks (n = 5). Most common grade 3/4 adverse events were aspartate aminotransferase increase (8.9%) and γ-glutamyltransferase increase (8.9%). By biomarker analysis, patients with moderate AR expression of IHC (26%-75%), PIK3CA pathogenic mutations, or <60 ng/ml cell-free DNA yield showed longer PFS. CONCLUSION: Proxalutamide showed promising anti-tumour activity with good tolerability in patients with heavily pretreated AR+ mBC, supporting further investigation. TRIAL REGISTRATION: This clinical study was prospectively registered at chinadrugtrials.org.cn (Identifier: CTR20170757) and clinical trials.gov (Identifier: NCT04103853).

High-resolution structures of inhibitor complexes of human indoleamine 2,3-dioxygenase 1 in a new crystal form.

Human indoleamine 2,3-dioxygenase 1 (IDO1) is a heme-dependent enzyme with important roles in many cellular processes and is a potential target for drug discovery against cancer and other diseases. Crystal structures of IDO1 in complex with various inhibitors have been reported. Many of these crystals belong to the same crystal form and most of the reported structures have resolutions in the range 3.2-2.3 Å. Here, three new crystal forms of human IDO1 obtained by introducing a surface mutation, K116A/K117A, distant from the active site are reported. One of these crystal forms diffracted to 1.5 Šresolution and can be readily used for soaking experiments to determine high-resolution structures of IDO1 in complex with the substrate tryptophan or inhibitors that coordinate the heme. In addition, this mutant was used to produce crystals of a complex with an inhibitor that targets the apo form of the enzyme under the same conditions; the structure of this complex was determined at 1.7 Šresolution. Overall, this mutant represents a robust platform for determining the structures of inhibitor and substrate complexes of IDO1 at high resolution.

Structural determinants of the BRCA1 : estrogen receptor interaction.

Previously, we showed that the BRCA1 protein interacts directly and functionally with estrogen receptor-alpha (ER-alpha), resulting in the inhibition of estradiol (E2)-stimulated ER-alpha transcriptional activity. The interaction sites were mapped to the N-terminus of BRCA1 (within amino acids (aa) 1-302) and the ligand-binding domain/activation function-2 (LBD/AF-2) region (within aa 282-420) of ER-alpha. In this study, we have further characterized the structure/function relationship for the BRCA1 : ER-alpha interaction. We found that the N-terminal RING domain (aa 20-64) is not required for the BRCA1 : ER-alpha interaction. We identified two separate contact points for ER-alpha, one within aa 1-100 and the other within aa 100-200 of BRCA1; and we showed that each of these BRCA1 peptides interacts with BRCA1 in vitro and in vivo. By using different fragments of the BRCA1 N-terminus, we found that aa 67-100 and 101-133 are required for the interaction with ER-alpha, but that aa 1-67 and 134-302 are dispensible. Previously, we showed that BRCA1 aa 1-302 does not inhibit E2-stimulated ER-alpha transcriptional activity but does bind to ER-alpha and acts as a dominant negative inhibitor of the full-length BRCA1 protein. Somewhat surprisingly, we found that BRCA1 aa 1-100 and BRCA1 aa 101-200 (but not aa 201-300) each inhibited ER-alpha activity, although not as efficiently as full-length BRCA1. Mutations within an HIV Rev-like nuclear export signal that resembles a nuclear receptor corepressor motif (aa 86-95) impaired the ability of both truncated (aa 1-100) and full-length (aa 1-1863) BRCA1 proteins to interact with and/or repress ER-alpha activity. Based on these findings, a partial BRCA1 : ER-alpha three-dimensional structure is proposed. The implications of these findings for understanding the BRCA1 : ER-alpha interaction are discussed.

Microenvironmental pH-modified solid dispersions to enhance the dissolution and bioavailability of poorly water-soluble weakly basic GT0918, a developing anti-prostate cancer drug: preparation, characterization and evaluation in vivo.

The aim of the present work was to design a pH-modified solid dispersion (pH(M)-SD) that can improve the dissolution and bioavailability of poorly water-soluble weakly basic GT0918, a developing anti-prostate cancer drug. To select the appropriate acidifiers, a solubility test was carried out first. Solid dispersions (SDs) containing GT0918 and polyvinylpyrrolidone (PVP) were prepared using a solvent evaporation method and were characterized using dissolution studies in different media. The solid states of the SDs were investigated using scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and Fourier transformed infrared spectroscopy (FTIR). The in vivo pharmacokinetics of the pH(M)-SDs tablets were also studied in beagle dogs compared to the conventional tablets. The optimized pH(M)-SD (GT0918/PVP/citric acid, 1:2:2 weight ratio) exhibited a significant improvement in the dissolution behavior compared to both the physical mixture and the binary SDs. Solid-state characterization revealed that the amorphous formation of GT0918 in the SDs and the strong H-bonding were only found in the pH(M)-SDs containing citric acid. Furthermore, the GT0918-loaded pH(M)-SD tablets showed a higher AUC and a lower tmax compared to the conventional tablets. Accordingly, the pH(M)-SD might be an efficient route for enhancing the dissolution and bioavailability of poorly water-soluble GT0918.