Cortexolone 17α-propionate (clascoterone) is a novel androgen antagonist that is currently being analyzed in a large phase 2 clinical trial for the topical treatment of androgenetic alopecia (AGA). While the pathogenesis of AGA is still debated, the consensus is that AGA is an androgen-dependent hair disorder with strong genetic links, and that the testosterone metabolite, dihydrotestosterone (DHT), plays a causal role in its development. DHT binds to the androgen receptor (AR) in scalp dermal papilla cells (DPC) to induce AR-mediated transcription of genes that contribute to AGA in genetically predisposed individuals. Several studies have established that clascoterone is a potent antiandrogen that is well tolerated and has selective topical activity. The study described herein elucidates a potential mechanism of clascoterone in AGA. Clascoterone was found to inhibit AR-regulated transcription in a reporter cell line with similar efficacy to the 5α-reductase inhibitor, finasteride. More importantly, when compared with another direct AR antagonist, enzalutamide, clascoterone was significantly better at inhibiting IL-6 synthesis from DHT-stimulated primary cultures of human scalp DPC. Therefore, clascoterone may be an excellent candidate to be the first topical antiandrogen for treating AGA. J Drugs Dermatol. 2019;18(2):197-201.
Rifamycin SV is under development for treatment of travelers' diarrhea (TD) in a new oral formulation, Rifamycin SV MMX® (RIF‐MMX; Santarus Inc., San Diego, CA, USA), which targets its delivery to the colon, making it a unique rifamycin drug. This was a randomized, double‐blind, phase 3 study of adult travelers to Mexico or Guatemala experiencing acute diarrhea. A total of 264 patients received RIF‐MMX (2 × 200 mg twice daily for 3 days, n = 199) or placebo (n = 65) in a 3 : 1 ratio. The primary endpoint was the length of time between the administration of first dose of study drug and passage of the last unformed stool (TLUS; after which clinical cure was declared). Other endpoints included eradication of pathogens from the stools, pathogen minimum inhibitory concentration (MIC), and adverse events (AEs). TLUS was significantly shorter in the RIF‐MMX group (median: 46.0 hours) compared with placebo (median: 68.0 hours; p = 0.0008) and a larger percentage of RIF‐MMX treated patients (81.4%) achieved clinical cure compared with placebo patients (56.9%). TLUS was significantly shorter in the subgroups of patients with enteroaggregative, enterotoxigenic, or diffusely adherent Escherichia coli infections (p = 0.0035) with nonsignificant activity against invasive bacteria (p = 0.3804). Overall pathogen eradication rates were numerically higher in the RIF‐MMX group (67.0%) compared with placebo (54.8%) but the difference did not reach significance (p = 0.0836). In vitro resistance to rifamycin SV was observed in some bacteria remaining after treatment of patients with RIF‐MMX but was not associated with lower efficacy in them. AEs appeared to be more frequent with placebo (38.5%) than with RIF‐MMX (29.6%). RIF‐MMX shortened the duration of TD in patients with a broad range of pathogens and was well tolerated. The unique pharmacokinetic properties of the drug offer evidence that TD pathogens work at the level of the colon.
A series of new cortexolone-related derivatives has been synthesized and investigated for potential anti-androgenic activity. Among the steroids evaluated, 9,11-dehydrocortexolone 17a-butyrate (CB-03-04) was the most promising one. The compound displayed a strong local anti-androgenic activity in hamster’s flank organ test, and it was also found to be effective in the rat after subcutaneous injection. When compared to other well known androgen antagonists, the rank order of topical anti-androgenic activity in that test was: cyproterone acetate (CAS 427-51-0) ≥ CB-03-04 > finasteride (CAS 98319-26-7) > flutamide (CAS 13311-84-7). In addition, the steroid had selective antigonadotropic activity, when injected into parabiotic rats, and was about as active as progesterone. The activity of CB-03-04 was ascribed mainly to its ability to compete with the stimulating effects of testosterone and dihydrotestosterone and, concurrently, to inhibit the gonadotropins hypersecretion. This bimodal mechanism of action could be predictive for the clinical usefulness of the steroid in the treatment of prostate cancer and benign prostate hypertrophy.
Rifamycin SV is a broad-spectrum, poorly absorbed antimicrobial agent that, when coupled with MMX technology, is being targeted for the oral treatment of traveler's diarrhea (TD) and Clostridium difficile-associated disease (CDAD). Rifamycin SV was tested for activity against 911 TD-associated enteropathogens and 30 C. difficile isolates collected from several global surveillance studies. Rifamycin SV demonstrated similar antimicrobial activity levels against the Enterobacteriaceae, with MIC₅₀ values ranging from 32 to 128 μg/ml for all but one strain (an enterotoxigenic Escherichia coli at >512 μg/ml). For non-Enterobacteriaceae strains, MIC₅₀ values ranged from 2 to 8 μg/ml, with the exception of Campylobacter spp., for which all strains had MIC values of >512 μg/ml. Rifamycin SV also demonstrated excellent activity (MIC₅₀ of ≤ 0.03 μg/ml) against most C. difficile strains (including one hypervirulent NAP1 strain), and this activity was even superior to the potency observed for vancomycin, metronidazole, and rifaximin. In mutational passaging studies, rifamycin SV induced stable resistance and showed a mutation frequency in E. coli similar to that of rifampin. This study presents the potency of rifamycin SV for enteropathogens commonly recovered from patients with TD and CDAD. Additional in vitro and in vivo studies appear necessary to determine the utility of rifamycin SV as an oral agent for the prevention and treatment of TD and CDAD.
Extracellular nucleotides exert an important role in controlling cell physiology by activating intracellular signalling cascades. Osteoblast HOBIT cells express P2Y1 and P2Y2 G-protein-coupled receptors, and respond to extracellular ATP by increasing cytosolic calcium concentrations. Early growth response protein 1 (Egr-1) is a C2H2-zinc-finger-containing transcriptional regulator responsible for the activation of several genes involved in the control of cell proliferation and apoptosis, and is thought to have a central role in osteoblast biology. We show that ATP treatment of HOBIT cells increases Egr-1 protein levels and binding activity via a mechanism involving a Ca2+-independent protein kinase C isoform. Moreover, hypotonic stress and increased medium turbulence, by inducing ATP release, result in a similar effect on Egr-1. Increased levels of Egr-1 protein expression and activity are achieved at very early times after stimulation (5 min), possibly accounting for a rapid way for changing the osteoblast gene-expression profile. A target gene for Egr-1 that is fundamental in osteoblast physiology, COL1A2, is up-regulated by ATP stimulation of HOBIT cells in a timescale that is compatible with that of Egr-1 activation.
