Sotrastaurin, a novel small molecule inhibiting protein kinase C: first clinical results in renal-transplant recipients

Report of a joint ESOT and AST meeting: highlights in biologic agents and transplantation

A joint meeting organized by the European (ESOT) and American (AST) Societies of Transplantation occurred in Nice, France, October 1-3, 2010. Focused on emerging use of biologic agents in solid organ transplantation, it served as a venue for state-of-the-art updates in basic immunology and clinical science, with an emphasis on the interrelatedness of the two. This meeting summary is designed to highlight important insights communicated in Nice, offer an overview of novel therapeutics in development, and entice members of all societies to consider attending a second joint symposium, under consideration for 2012.

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.

Protein kinase C inhibitor sotrastaurin selectively inhibits the growth of CD79 mutant diffuse large B-cell lymphomas

The activated B-cell-like (ABC) subtype of diffuse large B-cell lymphoma (DLBCL) correlates with poor prognosis. The ABC subtype of DLBCL is associated with constitutive activation of the NF-κB pathway, and oncogenic lesions have been identified in its regulators, including CARD11/CARMA1 (caspase recruitment domain-containing protein 11), A20/TNFAIP3, and CD79A/B. In this study, we offer evidence of therapeutic potential for the selective PKC (protein kinase C) inhibitor sotrastaurin (STN) in preclinical models of DLBCL. A significant fraction of ABC DLBCL cell lines exhibited strong sensitivity to STN, and we found that the molecular nature of NF-κB pathway lesions predicted responsiveness. CD79A/B mutations correlated with STN sensitivity, whereas CARD11 mutations rendered ABC DLBCL cell lines insensitive. Growth inhibitory effects of PKC inhibition correlated with NF-κB pathway inhibition and were mediated by induction of G₁-phase cell-cycle arrest and/or cell death. We found that STN produced significant antitumor effects in a mouse xenograft model of CD79A/B-mutated DLBCL. Collectively, our findings offer a strong rationale for the clinical evaluation of STN in ABC DLBCL patients who harbor CD79 mutations also illustrating the necessity to stratify DLBCL patients according to their genetic abnormalities.

Evaluation of the novel protein kinase C inhibitor sotrastaurin as immunosuppressive therapy after renal transplantation

IMPORTANCE OF THE FIELD

The prevalence of acute renal allograft rejection has decreased substantially in past decades due to new and more specific immunosuppressive compounds but improvements in long-term graft function have not been achieved. There is a large need for new immunosuppressive agents that lack toxicity of current agents such as calcineurin inhibitors but show high synergistic efficiency in preventing rejection processes.

AREAS COVERED IN THIS REVIEW

This review summarizes data concerning the pharmacokinetics, pharmacodynamics and clinical efficacy of the new PKC inhibitor sotrastaurin with a focus on renal transplantation. The article contains information that has been presented at international transplant meetings and congresses and that has been published between 2006 and 2010. Additionally, current ongoing trials are described in detail.

WHAT THE READER WILL GAIN

Immunosuppressive regimens after kidney transplantation consist of a combination of several agents in order to minimize drug toxicity. Therefore, the reader is presented with the most up-to-date/current developments in sotrastaurin applications in Phase I and II trials with emphasis on data maintained from studies that combined sotrastaurin with established agents such as mycophenolic acid and tacrolimus.

TAKE HOME MESSAGE

Several trials are ongoing and planned to determine the optimal immunosuppressive regimen to benefit from sotrastaurin's distinct mechanism of action.

Alternatives to calcineurin inhibition in renal transplantation: belatacept, the first co-stimulation blocker

In the early 1990s, Linsley and colleagues produced a soluble fusion protein, comprising of the extracellular domain of cytotoxic T lymphocyte antigen (CTLA)4 and the human IgG1 Fc domain. Since then, several hundreds of scientific publications have demonstrated that CTLA4–Ig blocks CD28-mediated co-stimulation and suppresses unwanted T cell-mediated responses in animal models of transplantation, autoimmunity and inflammation. In the past two decades, Bristol-Myers Squibb Co. has developed abatacept, a CTLA4–Ig molecule for treating psoriasis and rheumatoid arthritis, and belatacept, a second-generation, higher affinity CTLA4–Ig molecule for use in kidney transplantation. Belatacept represents a new class of transplantation immunosuppressants and potentially offers clinicians a breakthrough therapy to preserve kidney function in the long term and reduce the side effects of current immunosuppressive therapies.