Parenteral platforms for tunable, long-acting administration of a highly hydrophobic antiretroviral drug.

GSK2838232 (GSK8232) is a second-generation maturation inhibitor (MI) developed for the treatment of HIV with excellent broad-spectrum virological profiles. The compound has demonstrated promising clinical results as an orally administered agent. Additionally, the compound's physical and pharmacological properties present opportunities for exploitation as long-acting parenteral formulations. Despite unique design constraints including solubility and dose of GSK8232, we report on three effective tunable drug delivery strategies: active pharmaceutical ingredient (API) suspensions, ionic liquids, and subdermal implants. Promising sustained drug release profiles were achieved in rats with each approach. Additionally, we were able to tune drug release rates through a combination of passive and active strategies, broadening applicability of these formulation approaches beyond GSK8232. Taken together, this report is an important first step to advance long-acting formulation development for critical HIV medicines that do not fit the traditional profile of suitable long-acting candidates.

Improving the developability profile of pyrrolidine progesterone receptor partial agonists.

The previously reported pyrrolidine class of progesterone receptor partial agonists demonstrated excellent potency but suffered from serious liabilities including hERG blockade and high volume of distribution in the rat. The basic pyrrolidine amine was intentionally converted to a sulfonamide, carbamate, or amide to address these liabilities. The evaluation of the degree of partial agonism for these non-basic pyrrolidine derivatives and demonstration of their efficacy in an in vivo model of endometriosis is disclosed herein.

Design and synthesis of orally bioavailable serum and glucocorticoid-regulated kinase 1 (SGK1) inhibitors.

The lead serum and glucocorticoid-related kinase 1 (SGK1) inhibitors 4-(5-phenyl-1H-pyrrolo[2,3-b]pyridin-3-yl)benzoic acid (1) and {4-[5-(2-naphthalenyl)-1H-pyrrolo[2,3-b]pyridin-3-yl]phenyl}acetic acid (2) suffer from low DNAUC values in rat, due in part to formation and excretion of glucuronic acid conjugates. These PK/glucuronidation issues were addressed either by incorporating a substituent on the 3-phenyl ring ortho to the key carboxylate functionality of 1 or by substituting on the group in between the carboxylate and phenyl ring of 2. Three of these analogs have been identified as having good SGK1 inhibition potency and have DNAUC values suitable for in vivo testing.

Comparison of N,N'-diarylsquaramides and N,N'-diarylureas as antagonists of the CXCR2 chemokine receptor.

N,N'-diarylsquaramides were prepared and evaluated as antagonists of CXCR2. The compounds were found to be potent and selective antagonists of CXCR2. Significant differences in SAR was observed relative to the previously described N,N'-diarylurea series. As was the case in the N,N'-diarylurea series, placing sulfonamide substituent adjacent to the acidic phenol significantly reduced the clearance in rat pharmacokinetic studies.

Preclinical pharmacokinetic properties of the P-glycoprotein inhibitor GF120918A (HCl salt of GF120918, 9,10-dihydro-5-methoxy-9-oxo-N-[4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]phenyl]-4-acridine-carboxamide) in the mouse, rat, dog, and monkey.

GF120918A, the HCl salt of GF120918 (9,10-dihydro-5-methoxy-9-oxo-N-[4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl) ethyl]phenyl]-4-acridine-carboxamide), has been used both in vitro and in vivo as a tool inhibitor of P-glycoprotein (Pgp) to investigate the role of transporters in the disposition of various test molecules. However, to date, a detailed description of the preclinical pharmacokinetic properties of GF120918A has not been published. This investigation was performed to evaluate in vitro and in vivo pharmacokinetic properties of GF120918A in the mouse, rat, dog, and monkey and to evaluate the in vivo efficacy of GF120918A in modulating absorption and systemic exposure in the monkey. GF120918A demonstrated reasonable absorption and systemic exposure in each of the species studied, however, in rodents, administration of 300 mg/kg afforded a substantially less than linear increase in systemic exposure compared with 30 mg/kg. In accordance with its intestinal and hepatic exposure and potency against P-glycoprotein, GF120918A demonstrated marked modulation of erythromycin systemic exposure in the monkey, with no effect on propranolol, a negative control molecule. In vitro, GF120918A demonstrated high plasma protein binding across species, although a definitive protein binding evaluation was precluded by poor recovery, particularly in buffer and in mouse, rat, and dog plasma. GF120918A did not demonstrate potent inhibition of several human cytochrome P450 enzymes evaluated in vitro, with IC(50) values well above concentrations anticipated to be achieved in vivo. Together, these data confirm the utility of GF120918A as a tool P-glycoprotein inhibitor in preclinical species and offer additional guidance on preclinical dose regimens likely to produce P-glycoprotein-mediated effects.

Development of an in vivo preclinical screen model to estimate absorption and first-pass hepatic extraction of xenobiotics. II. Use of ketoconazole to identify P-glycoprotein/CYP3A-limited bioavailability in the monkey.

The effect of P-glycoprotein (Pgp) and/or CYP3A on the disposition of xenobiotics has been extensively investigated and is often of interest during drug discovery lead optimization. We have previously described a monkey pharmacokinetic screen to rapidly estimate absorption and first-pass extraction. In the present work, this monkey screen has been expanded to include an assessment of Pgp/CYP3A effects on absorption and first-pass extraction, using ketoconazole as a prototypic dual Pgp/CYP3A inhibitor. To generate a ketoconazole dosing regimen, the pharmacokinetics of ketoconazole were first determined in the monkey and were found to be consistent with that previously described in the rat, dog, and human. Dose-ranging experiments demonstrated that a single 10-mg/kg intraduodenal ketoconazole dose would provide an appropriate exposure; this dose was used throughout subsequent interaction experiments. Next, erythromycin and propranolol were explored as positive and negative control substrates for Pgp/CYP3A interactions, respectively. As anticipated, ketoconazole produced no change in the absorption or first-pass extraction of propranolol but resulted in a substantial increase in absorption and decrease in first-pass extraction of erythromycin. Finally, this ketoconazole-based monkey screen was deployed in a drug discovery setting, and examples of such use are presented. These experiments have allowed a more complete characterization of ketoconazole as a prototypic dual Pgp/CYP3A inhibitor and its use as a tool in a preclinical setting and further demonstrate the use of the monkey to investigate the role of Pgp/CYP3A in limiting the oral bioavailability of new drug candidates.

Phenylbutyrates as potent, orally bioavailable vitronectin receptor (integrin alphavbeta3) antagonists.

In our continuing efforts to identify small molecule vitronectin receptor antagonists, we have discovered a series of phenylbutyrate derivatives, exemplified by 16, which have good potency and excellent oral bioavailability (approximately 100% in rats). This new series is derived conceptually from opening of the seven-membered ring of SB-265123.

Assessment of oral bioavailability enhancing approaches for SB-247083 using flow-through cell dissolution testing as one of the screens.

SB-247083 is a potent, nonpeptidic, orally active, ETA-selective, endothelin receptor antagonist. The diacid form and three salts (monoarginine, diarginine and disodium) of SB-247083 were evaluated during the pre-clinical phase of development. The developability attributes (i.e. hygroscopicity, thermal behavior, aqueous solubility, and drug-excipient compatibility) of these compounds were evaluated. In addition to these attributes, the flow-through cell (FTC) dissolution testing (using USP Apparatus 4) was used as a screening technique to evaluate several SB-247083 formulations of the diacid and its salts. FTC dissolution testing offers two distinct advantages over the more traditional static-condition dissolution testing: (1) maintenance of sink conditions; and (2) the ability to change the dissolution medium during a dissolution run. The former advantage is especially important for poorly aqueous soluble drugs having associated dissolution-rate-limitations, and the latter advantage allows one to more closely simulate the pH gradient associated with transit through the GI tract. Based on the comparative dissolution data, three formulations were chosen for oral dosing in dogs. The reasonable correlation found between the FTC dissolution results and the oral bioavailability data demonstrate that FTC dissolution testing can be a valuable tool for aiding in salt (solid-state form) and formulation selection in the early stages of development of drug candidates.

Pharmacokinetics of SB-247083, a potent and selective endothelin(A) receptor antagonist, in the rat, dog, and monkey.

The endothelins (ET) are among the most potent vasoconstrictors identified to date, and have been implicated in such diseases as renal failure, pulmonary hypertension, atherosclerosis, and congestive heart failure. There is currently interest in developing selective antagonists of the ET-A subtype receptor, and one such antagonist is SB-247083 ((E)-[1-butyl-5-[2-(2-carboxyphenyl) methoxy-4-chlorophenyl]-1H-pyrazole-4-yl]-2-[5-methoxydihydrobenzofuran-6-yl]methyl]-2-propionic acid). This investigation was conducted to evaluate the preclinical pharmacokinetics of SB-247083. Clearance of SB-247083 was low to moderate in the rat and monkey, and high in the dog. Oral bioavailability of SB-247083 administered as a solid formulation of the free acid was 24% in the rat, but low in the dog (4%) and the monkey (2%). An extensive in vitro salt form and formulation screen resulted in the identification of a formulation containing the monoarginyl salt with improved dissolution properties. This formulation provided a 2- to 4-fold increase in oral bioavailability in each of the preclinical species. In the dog, this improvement was reversed by the pre-administration of 0.1 N HCl to normalize the achlorhydric fasting dog stomach. These data show that SB-247083 may have suitable drug properties for progression in development.