Drug-Disease Interaction and Time-Dependent Population Pharmacokinetics of Isatuximab in Relapsed/Refractory Multiple Myeloma Patients.

Isatuximab, a monoclonal antibody (mAb) of immunoglobulin G (IgG) isotype, specifically targets the cluster of differentiation 38 antigen overexpressed in malignant plasma cells. Isatuximab is used to treat multiple myeloma (MM), characterized by the excessive production of abnormal "myeloma proteins" (M-proteins) that may interact with therapeutic IgG mAb on the neonatal Fc receptor (FcRn)-mediated recycling pathway. The clinical pharmacology profile of isatuximab was investigated by population pharmacokinetics (PKs) modeling in 476 patients with MM who received 1-20 mg/kg isatuximab either as single agent or in combination with pomalidomide-dexamethasone in 4 clinical trials. Isatuximab PKs were characterized by a two-compartment model with parallel time-varying linear clearance (CL) and nonlinear elimination. Due to a mechanism-based drug-disease interaction, patients secreting IgG M-protein exhibited a twofold lower drug exposure compared with patients with non-IgG MM. No dose adjustment was required based on MM immunoglobulin type because efficacy and safety profiles were comparable between IgG and non-IgG MM subpopulations. ß2-microglobulin, body weight, sex, drug material, and race have a limited effect on drug exposure and do not require any dose adjustment. A typical 50% decrease in linear CL from initial treatment to steady-state was predicted, and this decrease correlated with the best overall response rate and was slower for patients with IgG MM. These findings suggest that the time-dependent effect of isatuximab is likely mediated by a combined factor of both disease state evolution and the perturbation of the FcRn-mediated recycling pathway.

Complete remission of skin lesions in a patient with subcorneal pustular dermatosis (Sneddon-Wilkinson disease) treated with antimyeloma therapy: association with disappearance of M-protein.

Subcorneal pustular dermatosis (SPD), or Sneddon-Wilkinson disease, is a rare pustular skin disease that follows a chronic relapsing course. A well-known association exists between SPD and IgA monoclonal gammopathy of undetermined significance (MGUS), which exists in up to 40% of cases. SPD has also been observed in patients with IgA myeloma. In SPD, direct and indirect immunofluorescence studies do not reveal in vivo bound IgA to the epithelial cell surface, in contrast to IgA pemphigus, which has similar clinicopathological features. Here we describe the case of a male patient with SPD and a concurrent IgA MGUS who had been treated with dapsone for 20 years with frequent relapses. Following development of multiple myeloma, the patient was treated with intensive antimyeloma treatment consisting of high-dose melphalan with autologous stem cell transplantation. This resulted in a complete remission of the myeloma with disappearance of the M-protein. In addition, a sustained remission of SPD was achieved without further treatment. Twenty-eight months after melphalan therapy the M-protein reappeared in the serum, and 2 months later SPD reappeared with histopathologically proven skin lesions at predilection sites. Presence and absence of skin lesions was found to correlate with the presence and absence of the M-protein in the serum. This is the first report of antimyeloma therapy inducing a long-lasting remission in SPD. The findings in this patient strongly suggest a causal role for circulating IgA antibodies in the pathogenesis of SPD. Antimyeloma treatment should be considered in patients with IgA MGUS-associated SPD refractory to other therapies.

New frontiers in the treatment of multiple myeloma.

Recent leaps in elucidating the biology of myeloma, particularly the intracellular pathways and the complex interaction with the bone marrow microenvironment, have resulted in an unprecedented surge of novel, targeted therapies and therapeutic regimens. There are currently over 30 new agents being tested in the treatment of multiple myeloma (MM). Many of these are novel, targeted agents that have demonstrated significant efficacy and prolonged survival. In this review, we summarize the current understanding of the mechanisms of action of novel therapies being tested in the preclinical and clinical settings in MM. These include agents that act directly on the intracellular signaling pathways, cell maintenance processes, and cell surface receptors. Finally, we present the clinical responses to some of these agents when used alone or in combination in clinical trials of patients with MM. Indeed, MM has become a model disease for the development of novel, therapeutic agents.