FDA Approval Summary: Alpelisib Plus Fulvestrant for Patients with HR-positive, HER2-negative, PIK3CA-mutated, Advanced or Metastatic Breast Cancer.

On May 24, 2019, the FDA granted regular approval to alpelisib in combination with fulvestrant for postmenopausal women, and men, with hormone receptor (HR)-positive, HER2-negative, phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA)-mutated, advanced or metastatic breast cancer as detected by an FDA-approved test following progression on or after an endocrine-based regimen. Approval was based on the SOLAR-1 study, a randomized, double-blind, placebo-controlled trial of alpelisib plus fulvestrant versus placebo plus fulvestrant. The primary endpoint was investigator-assessed progression-free survival (PFS) per RECIST v1.1 in the cohort of trial participants whose tumors had a PIK3CA mutation. The estimated median PFS by investigator assessment in the alpelisib plus fulvestrant arm was 11 months [95% confidence interval (CI), 7.5-14.5] compared with 5.7 months (95% CI, 3.7-7.4) in the placebo plus fulvestrant arm (HR, 0.65; 95% CI, 0.50-0.85; two-sided P = 0.001). The median overall survival was not yet reached for the alpelisib plus fulvestrant arm (95% CI, 28.1-NE) and was 26.9 months (95% CI, 21.9-NE) for the fulvestrant control arm. No PFS benefit was observed in trial participants whose tumors did not have a PIK3CA mutation (HR, 0.85; 95% CI, 0.58-1.25). The most common adverse reactions, including laboratory abnormalities, on the alpelisib plus fulvestrant arm were increased glucose, increased creatinine, diarrhea, rash, decreased lymphocyte count, increased gamma glutamyl transferase, nausea, increased alanine aminotransferase, fatigue, decreased hemoglobin, increased lipase, decreased appetite, stomatitis, vomiting, decreased weight, decreased calcium, decreased glucose, prolonged activated partial thromboplastin time, and alopecia.

A Regulatory Perspective on Manufacturing Processes Pertaining to Lyophilized Injectable Products.

Freeze-drying, also known as lyophilization, is a dehydration process designed to prolong the shelf life of injectable drug products. Here, we provide regulatory considerations for manufacturing processes specific to lyophilized injectable products. Specifically, a general discussion on each unit operation, including compounding, filtration, filling, and lyophilization, is provided to help the pharmaceutical industry establish reliable manufacturing processes from a regulatory perspective. In addition, a list of manufacturing-related deficiencies identified from a total of 263 new drug applications (NDAs) and abbreviated new drug applications (ANDAs) submitted for lyophilized injectable products is provided. We hope that the information presented in this report may help applicants avoid some common manufacturing-related deficiencies in regulatory submissions, thereby making high-quality lyophilized pharmaceuticals expeditiously available to the American public.

Potent antiproliferative effects of 25-hydroxy-16-ene-23-yne-vitamin D3 that resists the catalytic activity of both CYP27B1 and CYP24A1.

The potency of 25-hydroxyvitamin D3 (25(OH)D3) is increased by several fold through its metabolism into 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) by cytochrome P450 27B1 (CYP27B1). Thus, the pivotal role of 1α-hydroxylation in the activation of vitamin D compounds is well known. Here, we examined the metabolism of 25-hydroxy-16-ene-23-yne-vitamin D3 (25(OH)-16-ene-23-yne-D3), a synthetic analog of 25(OH)D3 in a cell-free system and demonstrated that 25(OH)-16-ene-23-yne-D3 is neither activated by CYP27B1 nor inactivated by cytochrome P450 24A1 (CYP24A1). These findings were also confirmed in immortalized normal human prostate epithelial cells (PZ-HPV-7) which are known to express both CYP27B1 and CYP24A1, indicating that the structural modifications featured in 25(OH)-16-ene-23-yne-D3 enable the analog to resist the actions of both CYP27B1 and CYP24A1. To provide intelligible structure-function information, we also performed molecular docking analysis between the analog and CYP27B1. Furthermore, 25(OH)-16-ene-23-yne-D3 was found to suppress the growth of PZ-HPV-7 cells with a potency equivalent to 1α,25(OH)2D3. The antiproliferative activity of 25(OH)-16-ene-23-yne-D3 was found to be vitamin D receptor (VDR)-dependent as it failed to inhibit the growth of mammary tumor cells derived from VDR-knockout mice. Furthermore, stable introduction of VDR into VDR-knockout cells restored the growth inhibition by 25(OH)-16-ene-23-yne-D3. Thus, we identified 25-hydroxy-16-ene-23-yne-vitamin D3 as a novel non-1α-hydroxylated vitamin D analog which is equipotent to 1α,25(OH)2D3 in its antiproliferative activity. We now propose that the low potency of the intrinsic VDR-mediated activities of 25(OH)D3 can be augmented to the level of 1α,25(OH)2D3 without its activation through 1α-hydroxylation by CYP27B1, but by simply preventing its inactivation by CYP24A1.

Probing the intracellular glutathione redox potential by in-cell NMR spectroscopy.

Non-invasive and real-time analysis of cellular redox processes has been greatly hampered by lack of suitable measurement techniques. Here we describe an in-cell nuclear magnetic resonance (NMR) based method for measuring the intracellular glutathione redox potential by direct and quantitative measurement of isotopically labeled glutathione introduced exogenously into living yeast. By using this approach, perturbations in the cellular glutathione redox homeostasis were also monitored as yeast cells were subjected to oxidative stress.

Metabolic stability of 3-epi-1α,25-dihydroxyvitamin D3 over 1 α 25-dihydroxyvitamin D3: metabolism and molecular docking studies using rat CYP24A1.

3-epi-1α,25-dihydroxyvitamin D3 (3-epi-1α,25(OH)2D3), a natural metabolite of 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3), exhibits potent vitamin D receptor (VDR)-mediated actions such as inhibition of keratinocyte growth or suppression of parathyroid hormone secretion. These VDR-mediated actions of 3-epi-1α,25(OH)2D3 needed an explanation as 3-epi-1α,25(OH)2D3, unlike 1α,25(OH)2D3, exhibits low affinity towards VDR. Metabolic stability of 3-epi-1α,25(OH)2D3 over 1α,25(OH)2D3 has been hypothesized as a possible explanation. To provide further support for this hypothesis, we now performed comparative metabolism studies between 3-epi-1α,25(OH)2D3 and 1α,25(OH)2D3 using both the technique of isolated rat kidney perfusion and purified rat CYP24A1 in a cell-free reconstituted system. For the first time, these studies resulted in the isolation and identification of 3-epi-calcitroic acid as the final inactive metabolite of 3-epi-1α,25(OH)2D3 produced by rat CYP24A1. Furthermore, under identical experimental conditions, it was noted that the amount of 3-epi-calcitroic acid produced from 3-epi-1α,25(OH)2D3 is threefold less than that of calcitroic acid, the analogous final inactive metabolite produced from 1α,25(OH)2D3 . This key observation finally led us to conclude that the rate of overall side-chain oxidation of 3-epi-1α,25(OH)2D3 by rat CYP24A1 leading to its final inactivation is slower than that of 1α,25(OH)2D3. To elucidate the mechanism responsible for this important finding, we performed a molecular docking analysis using the crystal structure of rat CYP24A1. Docking results suggest that 3-epi-1α,25(OH)2D3, unlike 1α,25(OH)2D3, binds to CYP24A1 in an alternate configuration that destabilizes the formation of the enzyme-substrate complex sufficiently to slow the rate at which 3-epi-1α,25(OH)2D3 is inactivated by CYP24A1 through its metabolism into 3-epi-calcitroic acid.

Quantitative measurements of glutathione in yeast cell lysate using 1H NMR.

Methods for quantifying the level of glutathione (GSH) in yeast cell lysate are described using (1)H NMR analysis. For quantification purposes, the (1)H resonances corresponding to the Cys ßCH2 of GSH were identified as having the fewest overlapping spectral interferences from lysate matrix components using GSH spiked yeast lysate samples. Two methods, standard addition based on peak integration and a spectral subtraction approach, were evaluated for quantifying GSH in lysate samples. The peak integration procedure required baseline estimation and a peak fitting step to correct for background interferences while the spectral subtraction procedure was comparatively straightforward. The level of GSH measured by (1)H NMR was in good agreement with the concentration measured by the DTNB-GSSG reductase recycling assay. The proposed NMR method can lead to a reliable quantitation of GSH and could be applicable to a variety of other analytes of interest in complex biological matrices.

Nanoscale plasmonic interferometers for multispectral, high-throughput biochemical sensing.

In this work, we report the design, fabrication, and characterization of novel biochemical sensors consisting of nanoscale grooves and slits milled in a metal film to form two-arm, three-beam, planar plasmonic interferometers. By integrating thousands of plasmonic interferometers per square millimeter with a microfluidic system, we demonstrate a sensor able to detect physiological concentrations of glucose in water over a broad wavelength range (400-800 nm). A wavelength sensitivity between 370 and 630 nm/RIU (RIU, refractive index units), a relative intensity change between ~10(3) and 10(6) %/RIU, and a resolution of ~3 × 10(-7) in refractive index change were experimentally measured using typical sensing volumes as low as 20 fL. These results show that multispectral plasmonic interferometry is a promising approach for the development of high-throughput, real-time, and extremely compact biochemical sensors.

A new insight into the role of rat cytochrome P450 24A1 in metabolism of selective analogs of 1α,25-dihydroxyvitamin D3.

We examined the metabolism of two synthetic analogs of 1α,25-dihydroxyvitamin D3 (1), namely 1α,25-dihydroxy-16-ene-23-yne-vitamin D3 (2) and 1α,25-dihydroxy-16-ene-23-yne-26,27-dimethyl-vitamin D3 (4) using rat cytochrome P450 24A1 (CYP24A1) in a reconstituted system. We noted that 2 is metabolized into a single metabolite identified as C26-hydroxy-2 while 4 is metabolized into two metabolites, identified as C26-hydroxy-4 and C26a-hydroxy-4. The structural modification of adding methyl groups to the side chain of 1 as in 4 is also featured in another analog, 1α,25-dihydroxy-22,24-diene-24,26,27-trihomo-vitamin D3 (6). In a previous study, 6 was shown to be metabolized exactly like 4, however, the enzyme responsible for its metabolism was found to be not CYP24A1. To gain a better insight into the structural determinants for substrate recognition of different analogs, we performed an in silico docking analysis using the crystal structure of rat CYP24A1 that had been solved for the substrate-free open form. Whereas analogs 2 and 4 docked similar to 1, 6 showed altered interactions for both the A-ring and side chain, despite prototypical recognition of the CD-ring. These findings hint that CYP24A1 metabolizes selectively different analogs of 1, based on their ability to generate discrete recognition cues required to close the enzyme and trigger the catalytic mechanism.