Robert T. Foster

Next-generation calcineurin inhibitors for ophthalmic indications

Calcineurin inhibitors (CNIs) are potent immunosuppressants that reversibly inhibit T-cell proliferation and prevent the release of pro-inflammatory cytokines by blocking the activity of calcineurin, a ubiquitous enzyme that is found in cell cytoplasm. CNIs can be highly effective in immune-mediated ophthalmic diseases such as uveitis, dry eye syndrome and inflammatory blepharitis, as well as for the prevention of rejection in corneal transplants. ISA-247/LX-211 is a novel CNI that is in Phase III clinical development for the treatment of various forms of non-infectious uveitis. ISA-247/LX-211 is a rationally designed analog of ciclosporin A that exhibits more predictable pharmacokinetic and pharmacodynamic properties and a 4-fold greater calcineurin inhibition than its parent compound, ciclosporin A. ISA-247/LX-211 has been observed to be effective, well-tolerated, and safe in early clinical trials, exhibiting a much wider therapeutic window compared with classic CNIs, such as ciclosporin A and tacrolimus. An alternative approach to widening the therapeutic window for the therapy of ophthalmic disorders lies in local delivery of CNIs through polymeric implants that release the drug over long periods of time. The silicone matrix episcleral implant LX-201 is in Phase III development at present for the prevention of rejection in high-risk cornea transplantation.

ISA247: quality of life results from a phase II, randomized, placebo-controlled study.

Background: Psoriasis is a chronic skin condition that can negatively affect a patients quality of life (QoL), often hindering social functioning. ISA247, a novel psoriatic agent, has shown clinical efficacy in moderate to severe psoriasis sufferers, but its effect on QoL is currently not reported. Objective: The objective of this study was to assess the effect of ISA247 on the QoL in patients with stable, plaque-type psoriasis. Methods: A phase II, randomized, double-blind, placebo-controlled, parallel-group, multicenter study assessed the effects of ISA247 doses of 0.5 mg/kg/d (n = 77) or 1.5 mg/kg/d (n = 83) compared with placebo (n = 41) for 12 weeks. QoL was assessed using the Dermatology Life Quality Index (DLQI) and Psoriasis Disability Index (PDI) scales. Results: ISA247 treatment (pooled groups) significantly improved QoL scores as assessed by both the DLQI and the PDI compared with those receiving placebo (p < .05). Treatment with the higher dose of 1.5 mg/kg/d demonstrated a significantly greater response to many of the QoL scales compared with the 0.5 mg/kg/d group (p < .05). Conclusions: ISA247 appears to improve the QoL while also providing effective treatment for chronic, moderate to severe, plaque-type psoriasis.

Development and validation of a LC/MS/MS method for quantifying the next generation calcineurin inhibitor, voclosporin, in human whole blood

A rapid, accurate, and reproducible liquid chromatography electrospray tandem mass spectrometry (LC/ESI-MS/MS) method was developed and validated for the therapeutic drug monitoring of voclosporin in human whole blood. Sample aliquots of 100muL were processed utilizing a protein precipitation procedure that contained a mixture of methanol, 0.2M ZnSO(4), and deuterated voclosporin internal standard. Supernatant was injected onto a Zorbax SB-C8, 2.1x12.5mm column (at 60 degrees C), and washed with water-acetonitrile, supplemented with 0.02% glacial acetic acid and 0.02mM sodium acetate, to remove poorly retained components. After washing, water-MeOH (with 0.02% glacial acetic acid and 0.02mM sodium acetate) was used to elute the voclosporin and internal standard to the Applied Biosystems/MDS-Sciex API3000 mass spectrometer for detection in multiple reaction monitoring. Analytical performance was assessed in the range of 1-200ng/ml in whole blood. This method has been used to quantify concentrations of voclosporin in whole blood from healthy volunteers participating in a pharmacokinetic study.

Cytochrome P450 3A and P‐glycoprotein drug–drug interactions with voclosporin

AIMS Voclosporin is a novel calcineurin inhibitor intended for prevention of organ graft rejection and treatment of lupus nephritis. Pharmacokinetic drug interactions between voclosporin and a CYP3A inhibitor, inducer and substrate and a P-glycoprotein inhibitor and substrate were evaluated. METHODS Voclosporin 0.4 mg kg(-1) was administered to 24 subjects in each of five studies, as follows: every 12 h (Q12H) alone and concomitantly with ketoconazole 400 mg once daily (QD); single dose before and single dose after rifampin 600 mg QD; Q12H where midazolam 7.5 mg was administered as a single dose alone before voclosporin and with last the dose of voclosporin; Q12H alone and concomitantly with verapamil 80 mg every 8 h; and Q12H with digoxin 0.25 mg QD. The noncompartmental pharmacokinetic parameters maximal concentration (Cmax ) and area under the concentration-time curve (AUC) were obtained, and geometric least squares mean ratios and 90% confidence intervals were evaluated. RESULTS Ketoconazole increased voclosporin Cmax (6.4-fold) and AUC (18-fold); rifampin reduced voclosporin AUC (0.9-fold); voclosporin did not change exposure of midazolam or α-hydroxy-midazolam; verapamil increased voclosporin Cmax (2.1-fold) and AUC (2.7-fold); and voclosporin increased digoxin Cmax (0.5-fold), AUC (0.25-fold) and urinary excretion (0.2-fold). CONCLUSIONS Administration of voclosporin concomitantly with strong inhibitors and inducers of CYP3A resulted in increased and decreased exposures, respectively, and should be considered contraindicated. Drug-drug interactions involving voclosporin and CYP3A substrates are not expected. Administration of voclosporin concomitantly with inhibitors and substrates of P-glycoprotein resulted in increased voclosporin and substrate exposures, respectively. Appropriate concentration and safety monitoring is recommended with co-administration of voclosporin and P-glycoprotein substrates and inhibitors.

Pharmacokinetics of voclosporin in renal impairment and hepatic impairment

Voclosporin is a novel calcineurin inhibitor intended for prevention of organ graft rejection and treatment of lupus nephritis. These studies evaluated the effect of renal or hepatic impairment on pharmacokinetics of voclosporin. Thirty‐three subjects were enrolled into 1 of 4 groups based on renal function as defined by creatinine clearance and 18 subjects were enrolled into 1 of 3 groups based on hepatic function defined by Child‐Pugh classes. Voclosporin 0.4 mg/kg was administered orally. Geometric mean ratios (renal/hepatic impairment‐to‐normal) and 90% confidence intervals for Cmax and AUC were calculated. A default no‐effect interval of 80–125% was set. Although 90% confidence intervals exceeded the no‐effect intervals for both parameters, individual Cmax and AUC plots indicate almost complete overlapping range of values for mild and moderate renal impairment and normal subjects. Severe renal impairment resulted in a 1.5‐fold increase in AUC without an increase in Cmax. Mild to moderate hepatic impairment resulted in a 1.5‐ to 2‐fold increase in voclosporin exposure. Voclosporin can be administered safely to patients with mild to moderate renal impairment without dose modification. Appropriate safety monitoring with concentration‐based adjustments in transplantation are recommended for patients with severe renal impairment, and for patients with hepatic impairment.

Population PKPD of voclosporin in renal allograft patients

The aims of this population‐pharmacokinetic/pharmacodynamic (POP‐PKPD) analysis of voclosporin in renal allograft patients were to build a POP‐PKPD model for voclosporin and calcineurin activity (CNa) and identify clinically relevant covariates that could assist dosing of the drug. POP‐PKPD modeling was performed using a stochastic approximation of the standard expectation maximization (SAEM) algorithm for nonlinear mixed‐effects as implemented in Monolix™ 3.2. Voclosporin whole blood concentrations were obtained from de novo renal allograft patients and assayed using a validated LC/MS/MS assay. CNa was measured using a 32P‐radiolabeled assay. A two‐compartment model with simultaneous sigmoid inhibitory Emax model was used to describe the PKPD relationship between voclosporin concentration and CNa. The POP‐PKPD model was then utilized to simulate an optimal initial dosing strategy. Eighty‐seven patients were included in the POP‐PKPD study. Population mean estimates (relative standard error, rse) for oral clearance (CL/F) and first compartment volume of distribution (V1), were 717 mL min−1 (35%) and 2010 mL (17%), respectively. Maximum CNa Inhibition (Imax), effective concentration (C50), and baseline immunosuppression (S0) were 0.87 pmol/min/mg (8.0%), 123 ng/mL (10%), and 1.15 pmol/min/mg (4.0%), respectively. Covariate analyses demonstrated that age and body surface area significantly influenced CL/F: CLi=717(Agei/48.8)−0.57(BSAi/1.99)1.1 , while serum triglycerides significantly altered S0: S0i=1.15(TRIGi/1.97)0.15 .

In Vitro Phase I Metabolism of CRV431, a Novel Oral Drug Candidate for Chronic Hepatitis B

The cytochrome P450-mediated Phase I in vitro metabolism of CRV431 was studied using selective chemical inhibition and recombinant human enzymes. Additionally, the metabolic profile of CRV431 in human, rat, and monkey liver microsomes was investigated. Liver microsomes were incubated for 0–80 min with CRV431, and the metabolite profile was assessed by electrospray ionization liquid chromatography mass spectrometry (ESI-LCMS). CRV431 was extensively metabolized through oxidation to produce various hydroxylated and demethylated species. Species identified included monohydroxylated CRV431 (two distinct products), dihydroxylated CRV431, demethylated CRV431 (two distinct products), demethylated and hydroxylated CRV431 (two distinct products), didemethylated and hydroxylated CRV431, and didemethylated and dihydroxylated CRV431. The magnitude of metabolism was greatest in monkey, followed by human, followed by rat. Importantly, all of the species identified in human microsomes were correspondingly identified in monkey and/or rat microsomes. Human liver microsome studies using selective chemical inhibition, as well as studies using recombinant human cytochrome P450 enzymes, revealed that the major enzymes involved are cytochromes P450 3A4 and 3A5. Enzymes 1A2, 2B6, 2C8, 2C9, 2C19, and 2D6 are not involved in the in vitro metabolism of CRV431. This information will be useful for the further development of CRV431 both preclinically and clinically.