Fulvestrant as a reference antiestrogen and estrogen receptor (ER) degrader in preclinical studies: treatment dosage, efficacy, and implications on development of new ER-targeting agents

Deciphering the drug delivery potential of Type1 lipid transfer protein from Citrus sinensis for enhancing the therapeutic efficacy of drugs

Type1 Non-specific Lipid Transfer Protein (CsLTP1) from Citrus sinensis is a small cationic protein possessing a long tunnel-like hydrophobic cavity. CsLTP1 performing membrane trafficking of lipids is a promising candidate for developing a potent drug delivery system. The present work includes in-silico studies and the evaluation of drugs binding to CsLTP1 using biophysical techniques along with the investigation of CsLTP1's ability to enhance the efficacy of drugs employing cell-based bioassays. The in-silico investigations identified Panobinostat, Vorinostat, Cetylpyridinium Chloride, and Fulvestrant with higher affinities and stability of binding to the hydrophobic pocket of CsLTP1. SPR studies revealed strong binding affinities of anticancer drugs, Panobinostat (KD = 1.40 μM) and Vorinostat (KD = 2.17 μM) to CsLTP1 along with the binding and release kinetics. CD and fluorescent spectroscopy revealed drug-induced conformational changes in CsLTP1. CsLTP1-associated drug forms showed remarkably enhanced efficacy in MCF-7 cells, representing increased cell cytotoxicity, intracellular ROS, reduced mitochondrial membrane potential, and up-regulation of proapoptotic markers than the free drugs employing qRT-PCR and western blot analysis. The findings demonstrate that CsLTP1 binds strongly to hydrophobic drugs to facilitate their transport, hence improving their therapeutic efficacy revealed by the in-vitro investigations. This study establishes an excellent foundation for developing CsLTP1-based efficient drug delivery system.

Phase 1 study of oral selective estrogen receptor degrader (SERD) amcenestrant (SAR439859), in Japanese women with ER-positive and HER2-negative advanced breast cancer (AMEERA-2)

BACKGROUND

This AMEERA-2 study evaluated the pharmacokinetics, efficacy, and safety of the oral selective estrogen receptor degrader amcenestrant as a monotherapy with dose escalation in Japanese postmenopausal women with advanced estrogen receptor-positive and human epidermal growth factor receptor 2-negative breast cancer.

METHODS

In this open-label, nonrandomized, phase I study, patients received amcenestrant 400 mg once daily (QD) (n = 7) and 300 mg twice daily (BID) (n = 3). The incidence of dose-limiting toxicities (DLT), recommended dose, maximum tolerated dose (MTD), pharmacokinetics, efficacy, and safety were assessed.

RESULTS

No DLTs were observed and MTD was not reached in the 400 mg QD group. One DLT (grade 3 maculopapular rash) was reported in a patient treated with 300 mg BID. After repeated oral administration of either dosing regimen, steady state reached before day 8, without accumulation. Four out of 5 response-evaluable patients from 400 mg QD group achieved clinical benefit and showed tumor shrinkage. No clinical benefit was reported in the 300 mg BID group. Overall, most patients (8/10) experienced a treatment-related adverse event (TRAE), with skin and subcutaneous tissue disorders most commonly reported (4/10 patients). No ≥ grade 3 TRAE in 400 mg QD group and 1 grade 3 TRAE in 300 mg BID group were reported.

CONCLUSIONS

Amcenestrant 400 mg QD has a favorable safety profile and has been selected as the recommended Phase II dose for monotherapy for evaluating the safety and efficacy of amcenestrant in a larger, global, randomized clinical trial of patients with metastatic breast cancer.

TRIAL REGISTRATION

Clinical trial registration NCT03816839.

Generation of 3D Spheroids Using a Thiol-Acrylate Hydrogel Scaffold to Study Endocrine Response in ER+ Breast Cancer

Culturing cancer cells in a three-dimensional (3D) environment better recapitulates in vivo conditions by mimicking cell-to-cell interactions and mass transfer limitations of metabolites, oxygen, and drugs. Recent drug studies have suggested that a high rate of preclinical and clinical failures results from mass transfer limitations associated with drug entry into solid tumors that 2D model systems cannot predict. Droplet microfluidic devices offer a promising alternative to grow 3D spheroids from a small number of cells to reduce intratumor heterogeneity, which is lacking in other approaches. Spheroids were generated by encapsulating cells in novel thiol–acrylate (TA) hydrogel scaffold droplets followed by on-chip isolation of single droplets in a 990- or 450-member trapping array. The TA hydrogel rapidly (∼35 min) polymerized on-chip to provide an initial scaffold to support spheroid development followed by a time-dependent degradation. Two trapping arrays were fabricated with 150 or 300 μm diameter traps to investigate the effect of droplet size and cell seeding density on spheroid formation and growth. Both trapping arrays were capable of ∼99% droplet trapping efficiency with ∼90% and 55% cellular encapsulation in trapping arrays containing 300 and 150 μm traps, respectively. The oil phase was replaced with media ∼1 h after droplet trapping to initiate long-term spheroid culturing. The growth and viability of MCF-7 3D spheroids were confirmed for 7 days under continuous media flow using a customized gravity-driven system to eliminate the need for syringe pumps. It was found that a minimum of 10 or more encapsulated cells are needed to generate a growing spheroid while fewer than 10 parent cells produced stagnant 3D spheroids. As a proof of concept, a drug susceptibility study was performed treating the spheroids with fulvestrant followed by interrogating the spheroids for proliferation in the presence of estrogen. Following fulvestrant exposure, the spheroids showed significantly less proliferation in the presence of estrogen, confirming drug efficacy.

Estradiol and Estrogen-like Alternative Therapies in Use: The Importance of the Selective and Non-Classical Actions

Estrogen is one of the most important female sex hormones, and is indispensable for reproduction. However, its role is much wider. Among others, due to its neuroprotective effects, estrogen protects the brain against dementia and complications of traumatic injury. Previously, it was used mainly as a therapeutic option for influencing the menstrual cycle and treating menopausal symptoms. Unfortunately, hormone replacement therapy might be associated with detrimental side effects, such as increased risk of stroke and breast cancer, raising concerns about its safety. Thus, tissue-selective and non-classical estrogen analogues have become the focus of interest. Here, we review the current knowledge about estrogen effects in a broader sense, and the possibility of using selective estrogen-receptor modulators (SERMs), selective estrogen-receptor downregulators (SERDs), phytoestrogens, and activators of non-genomic estrogen-like signaling (ANGELS) molecules as treatment.

Fulvestrant-3-Boronic Acid (ZB716) Demonstrates Oral Bioavailability and Favorable Pharmacokinetic Profile in Preclinical ADME Studies

Fulvestrant-3-boronic acid (ZB716), an oral selective estrogen receptor degrader (SERD) under clinical development, has been investigated in ADME studies to characterize its absorption, metabolism, and pharmacokinetics. ZB716 was found to have high plasma protein binding in human and animal plasma, and low intestinal mucosal permeability. ZB716 had high clearance in hepatocytes of all species tested. ZB716 was metabolized primarily by CYP2D6 and CYP3A. In human liver microsomes, ZB716 demonstrated relatively low inhibition of CYP1A2, 2C8, 2C9, 2C19, 2D6, and 3A4 (when testosterone was used as the substrate), and no inhibition of CYP2B6 and 3A4 (when midazolam was used as the substrate). In assays for enzyme activity, ZB716 induced CYP1A2, 2B6, and 3A4 in a concentration-dependent manner. Single-dose and repeated-dose pharmacokinetic studies in rats and dogs showed oral bioavailability, dose-proportional drug exposure, and drug accumulation as measured by maximum concentration and area under the concentration–time curve (AUC).