Discovery of 2,4-diamino-5-cyanopyrimidine derivatives as protein kinase C theta inhibitors with mitigated time-dependent drug-drug interactions

Protein kinase C theta (PKCθ) plays a critical role in T cell signaling and has therapeutic potential for T cell-mediated diseases such as transplant rejection and rheumatoid arthritis. PKCθ inhibitors have emerged as effective immunomodulative agents for the prevention of transplant rejection. We previously reported that the 2,4-diamino-5-cyanopyrimidine derivative 2 was a potent PKCθ inhibitor; however, it exhibited CYP3A4 time-dependent inhibition (TDI). Here, we report the structural modification of compound 2 into 34 focusing on mitigating CYP3A4 TDI. Compound 34 exhibited potent in vitro activity with mitigated CYP3A4 TDI and efficacy in vivo transplant model.

Implementation of highly sophisticated flow cytometry assays in multicenter clinical studies: considerations and guidance

Flow cytometry is increasingly becoming an important technology for biomarkers used in drug discovery and development. Within clinical development flow cytometry is used for the determination of PD biomarkers, disease or efficacy biomarkers or patient stratification biomarkers. Significant differences exist between flow cytometry methodology and other widely used technologies measuring soluble biomarkers including ligand binding and mass spectrometry. These differences include the very heavy reliance on aspects of sample processing techniques as well as sample stabilization to ensure viable samples. These differences also require exploration of new approaches and wider discussion regarding method validation requirements. This paper provides a review of the current challenges, solutions, regulatory environment and recommendations for the application of flow cytometry to measure biomarkers in clinical development.

Sotrastaurin (AEB071) alone and in combination with cyclosporine A prolongs survival times of non-human primate recipients of life-supporting kidney allografts

BACKGROUND

Sotrastaurin (STN), a novel oral protein kinase C inhibitor that inhibits early T-cell activation, was assessed in non-human primate recipients of life-supporting kidney allografts.

METHODS

Cynomolgus monkey recipients of life-supporting kidney allografts were treated orally with STN alone or in combination with cyclosporine A (CsA).

RESULTS

STN monotherapy at 50 mg/kg once daily prolonged recipient survival times to the predefined endpoint of 29 days (n=2); when given at 25 mg/kg twice daily, the median survival time (MST) was 27 days (n=4). Neither once-daily monotherapy of STN 20 mg/kg nor CsA 20 mg/kg was effective (MST 6 days [n=2] and 7 days [n=5], respectively). In combination, however, STN 20 mg/kg and CsA 20 mg/kg prolonged MST to more than 100 days (n=5). By combining lower once-daily doses of STN (7 or 2 mg/kg) with CsA (20 mg/kg), MST was more than 100 (n=3) and 22 days (n=2), respectively. Neither in single-dose pharmacokinetic studies nor the transplant recipients were STN or CsA blood levels for combined treatment greater than when either drug was administered alone. STN blood levels in transplant recipients during combination therapy were dose related (20 mg/kg, 30-182 ng/mL; 7 mg/kg, 7-41 ng/mL; and 2 mg/kg, 3-5 ng/mL). STN at a daily dose of up to 20 mg/kg was relatively well tolerated.

CONCLUSIONS

STN prolonged survival times of non-human primate kidney allograft recipients both as monotherapy and most effectively in combination with CsA. Pharmacokinetic interactions were not responsible for the potentiation of immunosuppressive efficacy by coadministering STN and CsA.

Targets of new immunosuppressants in renal transplantation

Although current immunosuppression is highly effective in avoiding acute rejection, it is associated with nephrotoxicity, cardiovascular morbidity, infection, and cancer. Thus, new drugs dealing with new mechanisms, as well as minimizing comorbidities, are warranted in renal transplantation. Few novel drugs are currently under investigation in Phase I, II, or III clinical trials. Belatacept is a humanized antibody that inhibits T-cell co-stimulation and has shown encouraging results in Phase II and III trials. Moreover, two new small molecules are under clinical development: AEB071 or sotrastaurin (a protein kinase C inhibitor) and CP-690550 or tasocitinib (a Janus kinase inhibitor). Refinement in selecting the best combinations for the new and current immunosuppressive agents is probably the main challenge for the next few years.

The effects of AEB071 (sotrastaurin) with tacrolimus on rat heterotopic cardiac allograft rejection and survival

BACKGROUND

AEB071 (sotrastaurin) is a specific inhibitor of protein kinase C that prevents T-cell activation. Our previous study demonstrated that AEB071 monotherapy could prevent acute cardiac allograft rejection in rats. Herein, we investigated the effects of AEB071 combined with various doses of tacrolimus (Tac) on the allograft rejection and survival in a rat heart transplantation model.

MATERIALS AND METHODS

Heterotopic cardiac transplantation from Brown-Norway to Lewis rats was performed. Cardiac allograft survival was assessed by monitoring heartbeats in six recipients of each experimental group. Another four recipient rats were selectively sacrificed in each group at d 7 post-transplantation for histologic examination. Serum transaminases, blood urea nitrogen, and creatinine concentrations were measured.

RESULTS

AEB071 monotherapy prolonged allograft mean survival time (MST) compared with the untreated control group. Also a combination of AEB071 and Tac prolonged MST compared with monotherapy groups with higher dose of Tac. In the cardiac graft histology, AEB071 combined with Tac 0.6 mg/kg/d significantly decreased the rejection grade as indicative of decreased inflammatory cell infiltration into the graft. No experimental group was found with any abnormal histologic or serologic evidence of liver and kidney toxicity.

CONCLUSION

AEB071 combined with a smaller dosage of Tac may be clinically possible to establish calcineurin inhibitor (CNI) minimization protocol in solid organ transplantation.

In vivo CYP3A activity is significantly lower in cyclosporine-treated as compared with tacrolimus-treated renal allograft recipients

In vitro studies have identified cyclosporine and tacrolimus as CYP3A inhibitors. In the current study in renal allograft recipients, we used intravenously and orally administered midazolam as a drug probe to assess whether the study drugs at doses that are generally used in clinical practice have differential effects on in vivo hepatic and first-pass CYP3A activities. Systemic and apparent oral midazolam clearance were 24% (269 ± 73 vs. 354 ± 102 ml/min, P = 0.022) and 31% (479 ± 190 vs. 688 ± 265 ml/min, P = 0.013), respectively, lower in cyclosporine-treated patients (n = 20) than in matched tacrolimus-treated patients (n = 20). The latter displayed midazolam clearances similar to those in two larger cohorts of nonmatched tacrolimus-treated patients (n = 58 and n = 80) and to those receiving a calcineurin inhibitor-free regimen (n = 6). This implies that in vivo hepatic and first-pass CYP3A activities are significantly lower in patients receiving cyclosporine than in those receiving tacrolimus, indicating that, at the doses generally used in clinical practice, cyclosporine is the stronger of the two with respect to CYP3A inhibition. This observation has important implications in the context of drug-drug interactions in transplant recipients.

Pharmacokinetics of sotrastaurin combined with tacrolimus or mycophenolic acid in de novo kidney transplant recipients

BACKGROUND

Sotrastaurin is a protein kinase C inhibitor in the development for prevention of organ rejection after renal transplantation.

METHODS

In a multicenter phase 2 trial, 216 de novo renal transplant recipients were randomized to mycophenolic acid (MPA) with standard-exposure tacrolimus (treatment A, n=74), 200 mg sotrastaurin twice daily with standard-exposure tacrolimus (treatment B, n=76), or 200 mg sotrastaurin twice daily with reduced-exposure tacrolimus (treatment C, n=66). After month 3, tacrolimus was replaced with MPA in arms B and C. The longitudinal pharmacokinetics of sotrastaurin and tacrolimus were prospectively evaluated through month 6.

RESULTS

Sotrastaurin predose drug concentration (C0) was 0.6±0.4 μg/mL and did not differ when combined with standard-exposure versus reduced-exposure tacrolimus (P=0.99) nor when tacrolimus was replaced by MPA (P=0.11). Sotrastaurin peak concentration was 1.6±0.6 μg/mL, and area under the drug concentration-time curve over a dosing interval (AUC) was 12.2±4.2 μg hr/mL. Intersubject variability in AUC was 27% and not significantly influenced by age (18-67 years), weight (47-121 kg), sex, or creatinine clearance (36-173 mL/min). Sotrastaurin C0 was positively correlated with AUC (r=0.62, P<0.0001). Sotrastaurin increased tacrolimus concentrations by a pharmacokinetic interaction inasmuch as the tacrolimus dose needed to achieve a given C0 was up to 47% lower when combined with sotrastaurin versus with MPA.

CONCLUSIONS

Sotrastaurin pharmacokinetics were similar when combined with reduced-exposure or standard-exposure tacrolimus or with MPA. Tacrolimus exposure was significantly increased by sotrastaurin in the initial weeks posttransplant by a pharmacokinetic interaction.