Clinical pharmacology considerations for the approval of belimumab for the treatment of adult patients with active lupus nephritis: A regulatory perspective.

On 16 December 2020, FDA approved Benlysta® (belimumab) for both the intravenous (IV) and subcutaneous (SC) administration routes for the treatment of adult patients with active lupus nephritis (LN) who are receiving standard therapy. This approval represents the first FDA approved treatment of patients with active LN.The approved IV dosing regimen (10 mg/kg dose Q2W for three doses, then 10 mg/kg Q4W thereafter) was based on a randomized double-blind placebo controlled clinical trial in adult patients with LN. For the approval of the SC dosing regimen (400 mg dose QW for four doses, then 200 mg QW thereafter), efficacy was supported solely by pharmacokinetics (PK) modeling and simulation which estimated a matched steady state average concentration and higher trough concentrations for the SC administration route, for bridging to the efficacy of IV belimumab in adults with LN. The safety and immunogenicity profile of the SC administration route has been assessed in the SLE studies.In a population PK analysis, higher proteinuria was associated with greater belimumab clearance and lower belimumab exposure. In an exposure response analysis, the efficacy of belimumab as evaluated by renal response was mainly driven by patients with lower proteinuria at baseline regardless of other baseline characteristics (e.g. baseline renal function, renal biopsy classification), induction therapies, or belimumab exposure levels (within 10 mg/kg dosing regimen), etc. However, post hoc analyses showed that belimumab had activity in LN patients with higher proteinuria at baseline. There is no adequate information to suggest that a higher dose would provide additional benefit for patients with lower exposure (e.g. higher proteinuria).

Drug Interaction Between Febuxostat and Thiopurine Antimetabolites: A Review of the FDA Adverse Event Reporting System and Medical Literature.

BACKGROUND: There is a known drug interaction (DI) between xanthine oxidase (XO) inhibitors and the thiopurine immunosuppressants, azathioprine (AZA) and mercaptopurine (6-MP). Xanthine oxidase inhibition increases concentrations of AZA and 6-MP active metabolites, possibly resulting in myelosuppression. When allopurinol is used with AZA or 6-MP, dose reduction of AZA or 6-MP is recommended. Febuxostat is a newer XO inhibitor approved for the treatment of gout. OBJECTIVE: To determine the clinical impact of the febuxostat-thiopurine DI. DESIGN AND SETTING: Case series derived from the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) and published medical literature. PATIENTS: Nineteen patients who received concomitant febuxostat and either AZA or 6-MP. MEASUREMENTS: Laboratory and clinical data. RESULTS: Nineteen cases reporting myelosuppressive events were identified in patients receiving febuxostat with AZA or 6-MP. Eighteen cases were treated with the combination of AZA and febuxostat. A median of 1.6 months elapsed from initiation of the drug combination until discovery of the event. Sixteen cases required hospitalization; 15 reported administration of blood products. Thirteen cases reported resolution of the event with discontinuation of both drugs, two reported discontinuation of the thiopurine only, and one reported discontinuation of febuxostat only. LIMITATIONS: Thiopurine monotherapy may cause myelosuppression. Complications of immunosuppression that may contribute to the real-world morbidity and mortality associated with the febuxostat-thiopurine DI were not examined. Finally, FAERS data are limited by the voluntary nature of reporting. CONCLUSION: Current febuxostat labeling contraindicates concomitant administration of febuxostat with either AZA or 6-MP. This case series demonstrates that the DI can result in clinically significant adverse events and is supportive of current febuxostat labeling.

Use of tumor necrosis factor-alpha inhibitors during pregnancy among women who delivered live born infants.

PURPOSE: To describe the use of tumor necrosis factor-alpha inhibitors (TNFis) among pregnancies ending in a live birth and with a diagnosis of ankylosing spondylitis (AS), Crohn's disease (CD), juvenile idiopathic arthritis (JIA), psoriasis (PsO), psoriatic arthritis (PsA), rheumatoid arthritis (RA), or ulcerative colitis (UC). METHODS: We identified pregnancies among women aged 15 to 54 years between 01/01/2004 and 09/30/2015 from 16 health plans participating in Sentinel. We inferred indication using ICD-9-CM codes in the 183-day period before conception. We assessed proportion of infliximab, etanercept, adalimumab, certolizumab pegol, and golimumab by calendar year, indication, and maternal age, and compared them to proportions in an age-matched, indication-matched, and date-matched non-pregnant cohort. RESULTS: Among 19 681 pregnancies with at least one chronic inflammatory condition, 2990 (15.2%) received a TNFi. In both pregnancies and matched non-pregnant cohort, TNFi use was highest (34.4%; 55.8%) for PsA patients and lowest (6.2%; 13.4%) for PsO patients. Etanercept was most frequently used among AS/JIA/PsA/PsO/RA patients, while infliximab was the preferred TNFi for CD/UC patients. Except for infliximab and certolizumab, TNFi use during pregnancy decreased after the first trimester. Pregnancies among older pregnant women (45-54 years) were more likely to be treated compared with the matched non-pregnant cohort. CONCLUSION: There was a preference for etanercept among pregnancies with AS/JIA/PsA/PsO/RA, despite the availability of other TNFis. Decline in TNFi use after the first trimester may be related to the desire to reduce TNFis transplacental transfer and to minimize infection risk to the fetus or baby associated with live vaccine immunizations after birth.