Comparison of two cyclosporine formulations in healthy Middle Eastern volunteers: bioequivalence of the new Sigmasporin Microoral and Sandimmun Neoral

Absorption enhancement strategies in chitosan-based nanosystems and hydrogels intended for ocular delivery: Latest advances for optimization of drug permeation

Ophthalmic diseases can be presented as acute diseases like allergies, ocular infections, etc., or chronic ones that can be manifested as a result of systemic disorders, like diabetes mellitus, thyroid, rheumatic disorders, and others. Chitosan (CS) and its derivatives have been widely investigated as nanocarriers in the delivery of drugs, genes, and many biological products. The biocompatibility and biodegradability of CS made it a good candidate for ocular delivery of many ingredients, including immunomodulating agents, antibiotics, ocular hypertension medications, etc. CS-based nanosystems have been successfully reported to modulate ocular diseases by penetrating biological ocular barriers and targeting and controlling drug release. This review provides guidance to drug delivery formulators on the most recently published strategies that can enhance drug permeation to the ocular tissues in CS-based nanosystems, thus improving therapeutic effects through enhancing drug bioavailability. This review will highlight the main ocular barriers to drug delivery observed in the nano-delivery system. In addition, the CS physicochemical properties that contribute to formulation aspects are discussed. It also categorized the permeation enhancement strategies that can be optimized in CS-based nanosystems into four aspects: CS-related physicochemical properties, formulation components, fabrication conditions, and adopting a novel delivery system like implants, inserts, etc. as described in the published literature within the last ten years. Finally, challenges encountered in CS-based nanosystems and future perspectives are mentioned.

Generic Medicinal Products in Immunosuppressive Therapy-Should It be a Challenge for Therapeutic Drug Monitoring?

ABSTRACT

Immunosuppressants have a narrow therapeutic index (NTIDs). Indisputably cyclosporine, tacrolimus, everolimus, and sirolimus have NTIDs, and only in the case of mycophenolic acid, a scientific discussion has not been yet concluded. Their specificities highlight the implications for generics introduced into the drug market, more precisely, with bioequivalence testing. In the European Union, the European Medicines Agency (EMA) released the "Guideline on the Investigation of Bioequivalence." The bioequivalence (BE) of the generic (tested, T) versus original (reference, R) product should be confirmed by obtaining a 90% confidence interval (CI) for the T:R ratio of each of the 2 decisive pharmacokinetic parameters, namely, the area under the curve (AUC) between 90.00% and 111.11%. A similar approach (90.00%-112.00%) for AUC was adopted by the Canadian Agency for Drugs and Technologies in Health (CADTH) for NTIDs; however, the US Food and Drug Administration is still based on classic acceptance criteria: 90% CI between 80.00% and 125.00% but with special requirements of BE testing. A discussion about long-expected global consensus was performed in this study based on the literature concerning BE testing in the case of NTIDs. The narrow acceptance criteria reduce the potential mean difference in bioavailability between generic and original products by a few percent. To identify this problem, special attention has been paid to switching drugs (generic-generic, original-generic) and therapeutic drug monitoring after conversion (TDM). There is no global consensus on the acceptance criteria for the BE of generic drugs; therefore, consensus and harmonization are strictly necessary. This study presents a review of the generic drug market and its classification by manufacturers, drug agencies, and dates of marketing authorization. Guidelines for TDM optimization (during switching/conversion) have been proposed. Physicians and clinical pharmacists should pay special attention to switching immunosuppressive drugs between original versus generic formulations, and generic versus generic formulations. Patients and their families should be educated on the risks associated with uncontrolled conversion.

Bioavailability, Efficacy and Safety of Generic Immunosuppressive Drugs for Kidney Transplantation: A Systematic Review and Meta-Analysis

BACKGROUND

Concerns exist over the extrapolation of bioavailability studies of generic immunosuppressive drugs in healthy volunteers, regarding their efficacy and safety in kidney transplant recipients. We conducted a meta-analysis of trials examining the bioavailability of generic (test) immunosuppressive drugs relative to their brand (reference) counterparts in healthy volunteers, based on the US Food and Drug Administration requirements for approval of generics, and their efficacy and safety in kidney transplant recipients.

METHODS

Eligible studies were identified in PubMed, Cochrane Central Register of Controlled Trials, Scopus, ClinicalTrials.gov, and conference abstracts.

RESULTS

Twenty crossover trials of healthy volunteers (n = 641) and 6 parallel-arm randomized controlled trials of kidney transplant recipients (n = 594) were identified. The 90% CI of the pooled test-to-reference drug ratio for maximum or peak plasma concentration (Cmax) and area under the plasma concentration time-curve from time 0 to time of last determinable concentration (AUC(0-t)) fell within the required range (0.80-1.25) for cyclosporine (Cmax 0.91; 90% CI 0.86-0.95; and AUC(0-t) 0.97; 90% CI 0.94-1.00), tacrolimus (Cmax 1.17; 90% CI 1.09-1.24; and AUC(0-t) 1.00; 90% CI 0.97-1.03) and mycophenolate mofetil (Cmax 0.98; 90% CI 0.96-1.01; and AUC(0-t) 1.00; 90% CI 0.99-1.01). In subgroup analyses, some generic cyclosporine formulations did not meet criteria for bioequivalence. No significant differences were observed in the time to maximum plasma concentration and terminal plasma half-life between generic and brand drugs. In parallel-arm trials, generic cyclosporine was non-inferior to brand counterpart in terms of acute allograft rejection, infections, and death.

CONCLUSIONS

Not all generic immunosuppressive drugs have similar relative bioavailability to their brand name counterparts. Evidence on their efficacy and safety is inconclusive. Tighter regulatory requirement for approval of generic drugs with narrow therapeutic index is needed.

Therapeutic equivalence and mg:mg switch ability of a generic cyclosporine microemulsion formulation (Sigmasporin Microral) in stable renal transplant patients maintained on Sandimmun Neoral

We tested a hypothesized pharmacokinetic difference between the reference (Sandimmun Neoral) and test (Sigmasporin Microral) products to prove therapeutic equivalence in an open, multiple fixed dose, one-way crossover, multicenter, and multinational study over a period of 29 days. Forty two stable renal transplant recipients maintained on Sandimmun Neoral were enrolled. Whole blood was collected at day 14 of the study at 0, 0.5, 1.0, 1.5, 2, 3, 4, 5, 6, 8, 10, and 12 hours after reference dosing and the same schedule was repeated at day 29 after switching on an mg:mg basis to the test product at day 15 of the study. Analysis of variance was performed for the pharmacokinetic parameters (area under the curve [AUC]0-12, maximum concentration [Cmax]) of cyclosporine using log-transformed values. Tolerability was assessed by vital signs, adverse events, and laboratory investigations. The 90% confidence interval (CI) test for the Ln-transformed, pharmacokinetic parameters was all within the US Food and Drug Administration acceptable range of 80% to 125%, as Ln area under the steady-state curve (AUCss) was within the range of 92.56 to 103.55 and Ln Cmax was within the range of 85.73 to 103.58; the same also applied for AUC0-4, which may be considered the area of greatest inter- and intra-patient variability. Furthermore, in line with the newly adopted recommendations of the Expert Advisory Committee on Bioavailability and Bioequivalence of Health Canada, the 90% CI for AUCss was within the narrow range of 90% to 112%. No significant difference in tolerability was recorded between the two products. Sigmasporin Microral (Julphar) was found to be bioequivalent and clinically interchangeable on an mg:mg basis with Sandimmun Neoral (Novartis).

The Utility of the Population Approach Applied to Bioequivalence in Patients

Mixed-effect modeling was used to compare the population pharmacokinetics of 2 formulations of cyclosporine in patients. An open-label, multicenter, conversion study in stable, 6-month post-renal allograft recipients was conducted to compare the safety and pharmacokinetics of oral Pliva Cyclosporine Soft Gelatin Capsules (USP Modified) with Neoral (cyclosporine soft gelatin capsules, USP Modified) in stable post-renal transplant patients. Blood samples were collected predose and for 12 hours postdose on days 1, 14, 15, 28, and 29. Whole-blood samples were analyzed for cyclosporine using high-performance liquid chromatography and mass spectroscopy. Estimates of pharmacokinetic parameters were generated using noncompartmental and population compartmental pharmacokinetic analysis. Moreover, the effects of demographic factors on the pharmacokinetics of cyclosporine were evaluated using the nonlinear mixed-effects modeling program NONMEM. The rate and extent of bioavailability of cyclosporine did not differ between Pliva Cyclosporine Soft Gelatin Capsules and Neoral. In the final model, gender and actual body weight significantly affected the central and peripheral volumes of distribution. In addition, the pharmacokinetics of cyclosporine was defined robustly in this patient population using population pharmacokinetic approaches. Results indicate that the Pliva Cyclosporine Soft Gelatin Capsules and Neoral are bioequivalent when administered to renal transplant patients. Pliva Cyclosporine Soft Gelatin Capsules can then be substituted for Neoral in stabilized patients without anticipating dose adjustments.

Generic cyclosporine formulations: more open questions than answers

The introduction of cyclosporine (CsA) in clinical practice has significantly improved patient and allograft survival after organ transplantation. The new microemulsion CsA formulation, Neoral, has been associated with a more reproducible absorption and a better patient outcome as compared to the old formulation Sandimmune. Recently, several generic CsA formulations have been tested as bioequivalent to Neoral. Bioequivalence tests have been performed in selected groups of young, healthy male volunteers usually in single-dose studies, and then extended to completely different population, such as transplant recipients. However, growing body of evidence shows that CsA pharmacokinetics in healthy subjects is different from that of transplant patients, treated chronically with CsA. Therefore, converting patients from Neoral to the new generic formulations could be detrimental, exposing patients to increased risk of graft function deterioration and graft loss. Thus, more research and more accurate bioequivalence tests are required to address the unanswered problems dealing with the generic CsA formulations.