A mechanistic pharmacokinetic model with drug and antidrug antibody interplay, and its application for assessing the impact of immunogenicity response on bioequivalence testing

AIMS

Single-dose pharmacokinetic (PK) studies in healthy subjects have been the design of choice for bioequivalence determination for decades. This preference has been recently extended to PK similarity studies of proposed biosimilars. However, PK similarity studies can be complicated by the effect of immunogenicity response on drug disposition. The impact is exacerbated when there is an imbalance in host-specific immunological characteristics of subjects between the test and reference groups. Such complications remain poorly understood. The purpose of this communication is to show that the impact of immunogenicity response on PK similarity determination can be critical, using adalimumab as an example.

METHODS

Data for adalimumab concentrations and immunogenicity response over 10 weeks were obtained from 133 healthy subjects receiving a 40 mg dose of Humira® in a PK similarity study. Also, a population PK model with a mechanistic construct for delineating the interplay between adalimumab disposition and antidrug antibodies response was utilized to estimate via simulation the probability that a PK similarity study would fail in typical study settings.

RESULTS

The simulations showed that the immunogenicity response can have a profound impact on the outcome of PK similarity determination. As such, the probability of failing to achieve the similarity conclusion increased to 51.9%, from 13.8% in the absence of immunogenicity response.

CONCLUSION

This study provides a model-based framework for better understanding of how a PK similarity study can be optimally designed and for interpretation of the outcome of PK similarity determination when the drug disposition is affected in the presence of immunogenicity response.

Rheumatoid Arthritis Treatment. A Back to the Drawing Board Project or High Expectations for Low Unmet Needs?

Despite the significant progress in Rheumatoid Arthritis (RA) therapeutics, there are several reports in the literature claiming that the size of unmet needs in RA is large. In the era before biologics, there was indeed a significant number of patients who did not achieve low disease activity (LDA) or disease remission due to limited therapeutic choices in the doctors' armamentarium. Treatment wise, great progress has been achieved over the last decades with the discovery and introduction in therapeutics of new molecules, such as the biological (b) disease-modifying anti-rheumatic drugs (DMARDs), and the targeted synthetic (ts) DMARDs. Today, with such a plethora of conventional synthetic (cs) DMARDs, tsDMARDs, and bDMARDs, why are we unable to successfully treat RA patients? What is wrong? However, a new drug for RA does not mean it is necessary to switch to a new treatment. It is very easy to change and switch therapies when the patient complains about pain and stiffness. In this setting, it is obligatory to rule out other comorbidities and disorders that may be the cause of the pain first. Thus, clinicians must have a deep knowledge of the drug therapy and be able to adjust the treatment when needed. A minute clinical examination must be carried out on every visit with close monitoring of the patient. A treat-to-target (T2T) approach and the application of the American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) recommendations and strategies should minimize the unmet needs.

Tofacitinib in the treatment of moderate-to-severe rheumatoid arthritis: a cost-effectiveness analysis compared with adalimumab in Taiwan

Aims: Tofacitinib is an oral Janus kinase inhibitor for the treatment of rheumatoid arthritis (RA). This analysis investigated the cost-effectiveness of the second-line treatment with tofacitinib, compared with adalimumab, both plus methotrexate (MTX), in patients with moderate-to-severe RA and an inadequate response to the first-line MTX, from a Taiwan National Health Insurance Administration perspective. Materials and methods: A patient-level simulation model was used to project lifetime costs and quality-adjusted life-years (QALYs). Base-case analysis compared second-line treatment with tofacitinib 5 mg twice daily plus MTX vs adalimumab 40 mg every 2 weeks plus MTX. Patients switched or discontinued treatment due to a lack or loss of effectiveness or a serious adverse event. Efficacy was measured by change in Health Assessment Questionnaire-Disability Index (HAQ-DI) score. HAQ-DI scores were used to predict mortality and resource utilization, and were mapped onto utility values to estimate QALYs. Efficacy and safety data were derived from clinical trials and other secondary sources. Uncertainty in model parameters was explored using one-way deterministic and probabilistic sensitivity analyses. Results: Patients gained 0.09 more QALYs with second-line tofacitinib plus MTX compared with adalimumab plus MTX (5.13 vs 5.04, respectively) at an additional cost of New Taiwan Dollars (NT$) 12,881. The incremental cost-effectiveness ratio was NT$143,122/QALY. One-way sensitivity analysis confirmed the base-case result was robust. Limitations: The lack of available clinical data, particularly for HAQ-DI scores, may introduce some bias in the analysis. No patients were in an early stage of RA, which may limit the generalizability of these results. Base-case results from our study are not necessarily generalizable to countries with healthcare systems that differ considerably from Taiwan. Conclusions: From a payer perspective, second-line treatment with tofacitinib plus MTX is a cost-effective treatment strategy, compared with adalimumab plus MTX, in patients with moderate-to-severe RA in Taiwan.

Tofacitinib, an oral Janus kinase inhibitor, in patients from Brazil with rheumatoid arthritis: Pooled efficacy and safety analyses

BACKGROUND

Tofacitinib is an oral Janus kinase inhibitor for the treatment of rheumatoid arthritis (RA). Efficacy and safety of tofacitinib in Brazilian patients from Phase 2 (P2) and Phase 3 (P3) global studies of up to 24 months' duration were evaluated.

METHODS

Data were pooled from Brazilian patients with RA and an inadequate response to conventional synthetic or biologic disease-modifying antirheumatic drugs enrolled in P2/P3 tofacitinib studies who received tofacitinib 5 or 10 mg twice daily (BID), or placebo, as monotherapy or in combination with methotrexate. Efficacy, safety, and patient-reported outcomes were assessed over 24 months.

RESULTS

Patients (226) from Brazil were treated in tofacitinib global P2/P3 studies. At Month 3, there were improvements in American College of Rheumatology 20/50/70 response rates, Disease Activity Score in 28 joints, erythrocyte sedimentation rate, and Health Assessment Questionnaire-Disability Index scores with both tofacitinib doses. Improvements from baseline in pain, fatigue, and health-related quality of life with tofacitinib 5 and 10 mg BID were reported. Efficacy improvements were sustained up to Month 24. The most frequent class of adverse events was infections and infestations. No cases of tuberculosis or other opportunistic infections were reported.

CONCLUSION

In a Brazilian subpopulation of patients with RA, tofacitinib reduced disease signs and symptoms and improved physical function up to Month 24, with a safety profile consistent with findings from global studies.

Unmet needs in the treatment of rheumatoid arthritis. An observational study and a real-life experience from a single university center

OBJECTIVES

To estimate the size of unmet needs in the treatment of early Rheumatoid Arthritis (eRA), using all the conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) and/or biological DMARDs (bDMARDs) in a long-term observational study.

MATERIALS AND METHODS

538 patients with eRA were evaluated. The 2010 ACR/EULAR classification criteria were used. All patients were csDMARDs and bDMARDs-naive with disease duration less than one year. They were treated according to EULAR and ACR recommendations for RA. All the csDMARDs and bDMARDs were used. Clinical, laboratory findings with the disease activity score-28 and treatment decisions were all recorded as well as adverse drug reactions, reason of therapy termination, disease complications and comorbidities.

RESULTS

Methotrexate (58%) and Infliximab (37%) where the first csDMARD and bDMARD choice respectively. During follow-up, 14 patients were lost and 7 developed comorbidities. The final results are referred to 517 patients. Among those, 66% were treated with csDMARDs as monotherapy or in combination therapy with sustained low disease activity (LDA). However, 3.2% from this group neither achieved LDA, nor received bDMARDs, due to comorbidities. On the other hand, 34% were treated with bDMARDs with or without csDMARDs. The majority of them demonstrated sustained LDA. From this group, 17.7% never achieved LDA, despite that they switched and received all bDMARDs. Thus, 20.9% of our patients never achieved LDA.

CONCLUSIONS

Using the current recommendations for RA therapy we successfully treated the majority of our patients. However, we found that the size of gap and the unmet needs for treatment is about 20%.

The anti-CD6 antibody itolizumab provides clinical benefit without lymphopenia in rheumatoid arthritis patients: results from a 6-month, open-label Phase I clinical trial

Itolizumab is a humanized anti-CD6 monoclonal antibody (mAb) that has previously shown encouraging results, in terms of safety and positive clinical effects, in a 6-week monotherapy clinical trial conducted in rheumatoid arthritis (RA) patients. The current Phase I study evaluated the safety and clinical response for a longer treatment of 12 itolizumab intravenous doses in subjects with active RA despite previous disease-modifying anti-rheumatic drug (DMARD) therapy. Twenty-one subjects were enrolled into four dosage groups (0·1, 0·2, 0·4 and 0·8 mg/kg). Efficacy end-points including American College of Rheumatology (ACR)20, ACR50 and ACR70 response rates and disease activity score in 28 joints (DAS28) were monitored at baseline and at specific time-points during a 10-week follow-up period. Itolizumab was well tolerated up to the highest tested dose. No related serious adverse events were reported and most adverse events were mild. Remarkably, itolizumab treatment did not produce lymphopenia and, therefore, was not associated with infections. All patients achieved a clinical response (ACR20) at least once during the study. Eleven subjects (55%) achieved at least a 20% improvement in ACR just 1 week after the first itolizumab administration. The clinical response was observed from the beginning of the treatment and was sustained during 24 weeks. The efficacy profile of this 12-week treatment was similar to that of the previous study (6-week treatment). These results reinforce the safety profile of itolizumab and provide further evidence on the clinical benefit from the use of this anti-CD6 mAb in RA patients.

Sonodelivery Facilitates Sustained Luciferase Expression from an Episomal Vector in Skeletal Muscle

Successful gene delivery to skeletal muscle is a desirable goal, not only for treating muscle diseases, but also for immunization, treatment of metabolic disorders, and/or delivering gene expression that can treat systemic conditions, such as bone metastatic cancer, for example. Although naked DNA uptake into skeletal muscle is possible, it is largely inefficient in the absence of additional chemical or physical delivery methods. We describe a system for delivery of non-viral or plasmid DNA to skeletal muscle using ultrasound-assisted sonoporation of a nanoplex combining plasmid DNA and a branched polymer based on poly(cyclooctene-graft-oligopeptide). The materials and methods described herein promise to advance the field of sonodelivery and of gene delivery to muscle for therapeutic applications since a simple system is presented that enables long-term gene expression in vivo with the promise of a minimal inflammatory gene expression profile.