Phase 2 BELIEVE study part B: Efficacy and safety of rilzabrutinib for patients with pemphigus vulgaris

Targeting Bruton's tyrosine kinase (BTK) as a signaling pathway in immune-mediated diseases: from molecular mechanisms to leading treatments

Bruton's tyrosine kinase (BTK), a nonreceptor tyrosine kinase, plays a remarkable role in the transmission and amplification of extracellular signals to intracellular signaling pathways. Various types of cells use the BTK pathway to communicate, including hematopoietic cells particularly B cells and T cells. The BTK pathway plays a role in controlling the proliferation, survival, and functions of B cells as well as other myeloid cells. First, second, and third-generation BTK inhibitors are currently being evaluated for the treatment of immune-mediated diseases in addition to B cell malignancies. In this article, the available evidence on the action mechanisms of BTK inhibitors is reviewed. Then, the most recent data obtained from preclinical studies and ongoing clinical trials for the treatment of autoimmune diseases, such as pemphigus vulgaris, pemphigus foliaceus, bullous pemphigoid, systemic lupus erythematosus, Sjögren's disease, rheumatoid arthritis, systemic sclerosis, multiple sclerosis, myasthenia gravis, and inflammatory diseases such as psoriasis, chronic spontaneous urticaria, atopic dermatitis, and asthma are discussed. In addition, adverse effects and complications associated with BTK inhibitors as well as factors predisposing patients to BTK inhibitors complications are discussed.

Efficacy and Safety of Rilzabrutinib in Pemphigus: PEGASUS Phase 3 Randomized Study

TRIAL DESIGN

Pemphigus is a rare but life-threatening autoimmune disease requiring long-term treatment that minimizes corticosteroid (CS) exposure while providing consistent disease control. The phase 2 pemphigus study of oral, reversible, covalent Bruton tyrosine kinase inhibitor rilzabrutinib demonstrated rapid and sustained efficacy with well-tolerated safety.

METHODS

Adults (aged 18-80 years) were randomized 1:1 to 400 mg rilzabrutinib (n = 65) or placebo (n = 66) twice daily (with CS ≤ 0.5 mg/kg/d) for 37 weeks in the phase 3 PEGASUS study in moderate-to-severe pemphigus vulgaris/pemphigus foliaceus.

RESULTS

The primary endpoint of complete remission from week 29 to week 37 with the amended endpoint CS dose ≤10 mg/d was not significant for 13 of 54 (24%) rilzabrutinib versus 10 of 55 (18%) placebo patients with PV (P = .45). Secondary endpoints showed numerical but nonsignificant improvements with rilzabrutinib (vs placebo) in reduced CS use, prolonged complete remission duration, and faster time to first complete remission.

CONCLUSIONS

Overall, rilzabrutinib was well-tolerated, with similar adverse events reported in both groups. Using minimal CS dose ≤10 mg/d and excluding remote observations, the primary efficacy endpoint was not met. However, results from a prespecified sensitivity analysis using CS dose ≤5 mg/d, considering all observations, and including all patients support Bruton tyrosine kinase inhibition as a viable therapeutic approach for pemphigus.

Effects of Quinidine or Rifampin Co-administration on the Single-Dose Pharmacokinetics and Safety of Rilzabrutinib (PRN1008) in Healthy Participants

This open-label, phase 1 study was conducted with healthy adult participants to evaluate the potential drug-drug interaction between rilzabrutinib and quinidine (an inhibitor of P-glycoprotein [P-gp] and CYP2D6) or rifampin (an inducer of CYP3A and P-gp). Plasma concentrations of rilzabrutinib were measured after a single oral dose of rilzabrutinib 400 mg administered on day 1 and again, following a wash-out period, after co-administration of rilzabrutinib and quinidine or rifampin. Specifically, quinidine was given at a dose of 300 mg every 8 hours for 5 days from day 7 to day 11 (N = 16) while rifampin was given as 600 mg once daily for 11 days from day 7 to day 17 (N = 16) with rilzabrutinib given in the morning of day 10 (during quinidine dosing) or day 16 (during rifampin dosing). Quinidine had no significant effect on rilzabrutinib pharmacokinetics. Rifampin decreased rilzabrutinib exposure (the geometric mean of Cmax and AUC0-∞ decreased by 80.5% and 79.5%, respectively). Single oral doses of rilzabrutinib, with or without quinidine or rifampin, appeared to be well tolerated. These findings indicate that rilzabrutinib is a substrate for CYP3A but not a substrate for P-gp.

Autoimmune blistering diseases: promising agents in clinical trials

INTRODUCTION

Treatment options for autoimmune bullous diseases (AIBD) are currently limited to corticosteroids and traditional immunomodulants and immunosuppressants that are associated with unfavorable adverse effect profiles. The most frequent AIBDs, i.e. bullous pemphigoid, pemphigus vulgaris, and mucous membrane pemphigoid, impose a high disease burden onto affected patients and can be detrimental due to infections, exsiccosis, and impaired food intake. Significant progress has been made in elucidating disease mechanisms and key mediators by in vivo and in vitro models, thus identifying a multifaceted range of possible drug targets. However, except for rituximab for pemphigus vulgaris, no new drugs have been approved for the treatment of AIBDs in the last decades.

AREAS COVERED

This review covers new drug developments and includes ongoing or completed phase 2 and 3 clinical trials. Studies were identified by querying the registries of ClinicalTrials.gov and Cochrane Library.

EXPERT OPINION

Promising results were shown for a variety of new agents including nomacopan, efgartigimod, omalizumab, dupilumab, as well as chimeric autoantibody receptor T cells. Clinical translation in the field of AIBDs is highly active, and we anticipate significant advances in the treatment landscape.

New small molecules in dermatology: for the autoimmunity, inflammation and beyond

OBJECTIVE AND DESIGN

The discovery of new inflammatory pathways and the mechanism of action of inflammatory, autoimmune, genetic, and neoplastic diseases led to the development of immunologically driven drugs. We aimed to perform a narrative review regarding the rising of a new class of drugs capable of blocking important and specific intracellular signals in the maintenance of these pathologies: the small molecules.

MATERIALS/METHODS

A total of 114 scientific papers were enrolled in this narrative review.

RESULTS

We describe in detail the families of protein kinases-Janus Kinase (JAK), Src kinase, Syk tyrosine kinase, Mitogen-Activated Protein Kinase (MAPK), and Bruton Tyrosine Kinase (BTK)-their physiologic function and new drugs that block these pathways of intracellular signaling. We also detail the involved cytokines and the main metabolic and clinical implications of these new medications in the field of dermatology.

CONCLUSIONS

Despite having lower specificity compared to specific immunobiological therapies, these new drugs are effective in a wide variety of dermatological diseases, especially diseases that had few therapeutic options, such as psoriasis, psoriatic arthritis, atopic dermatitis, alopecia areata, and vitiligo.