Discovery of Axelopran (TD-1211): A Peripherally Restricted µ-Opioid Receptor Antagonist.

The effects of opioids in the central nervous system (CNS) provide significant benefit in the treatment of pain but can also lead to physical dependence and addiction, which has contributed to a growing opioid epidemic in the United States. Gastrointestinal dysfunction is an additional serious consequence of opioid use, and this can be treated with a localized drug distribution of a non-CNS penetrant, peripherally restricted opioid receptor antagonist. Herein, we describe the application of Theravance's multivalent approach to drug discovery coupled with a physicochemical property design strategy by which the N-substituted-endo-3-(8-aza-bicyclo[3.2.1]oct-3-yl)-phenyl carboxamide series of µ-opioid receptor antagonists was optimized to afford the orally absorbed, non-CNS penetrant, Phase 3 ready clinical compound axelopran (TD-1211) 19i as a potential treatment for opioid-induced constipation.

Fumaric acid microenvironment tablet formulation and process development for crystalline cenicriviroc mesylate, a BCS IV compound.

Cenicriviroc mesylate (CVC) is a potent dual antagonist of C-C chemokine receptor type 5 (CCR5) and C-C chemokine receptor type 2 (CCR2) in phase 2b development as an entry inhibitor for HIV-1 infection treatment.1,2 CVC is a weak base exhibiting BCS IV characteristics with a highly pH dependent solubility profile (>100 mg/mL for pH < 2 and <0.2 µg/mL for pH > 4) and low Caco-2 cell line permeability. Previous tablet formulations of CVC, including spray-dried dispersion and a wet granulation with citric acid, had been found unacceptable for commercial use due to chemical and physical instability or unacceptably high excipient loading precluding fixed-dose combinability. A high drug loading, 26% (w/w), acidic microenvironment tablet formulation with fumaric acid solubilizer (1:1 CVC/fumaric acid) and a dry granulation process was developed iteratively through a sequence of prototypes characterized by beagle dog absorption studies, focused beam reflectance measurement (FBRM), dynamic vapor sorption (DVS), and accelerated stability testing. The fumaric acid based dry granulated product demonstrated a mean bioavailability comparable to an oral solution dose in a dog model. Stability and moisture sensitivity of the formulation were improved via the dry granulation process technique and the use of fumaric acid. It is hypothesized that the observed slow dissolution kinetics of fumaric acid prolongs an acidic microenvironment around the agglomerated CVC crystals and excipients leading to increased CVC dissolution and thereby absorption. The fumaric acid formulation also demonstrated absorption resilience to gastric pH extremes in a dog model. This optimized formulation and process enables CVC to be a viable candidate for current HIV treatment paradigms of single once daily fixed-dose combination products.