Talquetamab, a T-Cell-Redirecting GPRC5D Bispecific Antibody for Multiple Myeloma

BACKGROUND

G protein-coupled receptor, family C, group 5, member D (GPRC5D) is an orphan receptor expressed in malignant plasma cells. Talquetamab, a bispecific antibody against CD3 and GPRC5D, redirects T cells to mediate killing of GPRC5D-expressing myeloma cells.

METHODS

In a phase 1 study, we evaluated talquetamab administered intravenously weekly or every other week (in doses from 0.5 to 180 μg per kilogram of body weight) or subcutaneously weekly, every other week, or monthly (5 to 1600 μg per kilogram) in patients who had heavily pretreated relapsed or refractory multiple myeloma that had progressed with established therapies (a median of six previous lines of therapy) or who could not receive these therapies without unacceptable side effects. The primary end points - the frequency and type of dose-limiting toxic effects (study part 1 only), adverse events, and laboratory abnormalities - were assessed in order to select the recommended doses for a phase 2 study.

RESULTS

At the data-cutoff date, 232 patients had received talquetamab (102 intravenously and 130 subcutaneously). At the two subcutaneous doses recommended for a phase 2 study (405 μg per kilogram weekly [30 patients] and 800 μg per kilogram every other week [44 patients]), common adverse events were cytokine release syndrome (in 77% and 80% of the patients, respectively), skin-related events (in 67% and 70%), and dysgeusia (in 63% and 57%); all but one cytokine release syndrome event were of grade 1 or 2. One dose-limiting toxic effect of grade 3 rash was reported in a patient who had received talquetamab at the 800-μg dose level. At median follow-ups of 11.7 months (in patients who had received talquetamab at the 405-μg dose level) and 4.2 months (in those who had received it at the 800-μg dose level), the percentages of patients with a response were 70% (95% confidence interval [CI], 51 to 85) and 64% (95% CI, 48 to 78), respectively. The median duration of response was 10.2 months and 7.8 months, respectively.

CONCLUSIONS

Cytokine release syndrome, skin-related events, and dysgeusia were common with talquetamab treatment but were primarily low-grade. Talquetamab induced a substantial response among patients with heavily pretreated relapsed or refractory multiple myeloma. (Funded by Janssen Research and Development; MonumenTAL-1 ClinicalTrials.gov number, NCT03399799.).

A semiphysiologically based pharmacokinetic modeling approach to predict the dose-exposure relationship of an antiparasitic prodrug/active metabolite pair

Dose selection during antiparasitic drug development in animal models and humans traditionally has relied on correlations between plasma concentrations obtained at or below maximally tolerated doses that are efficacious. The objective of this study was to improve the understanding of the relationship between dose and plasma/tissue exposure of the model antiparasitic agent, pafuramidine, using a semiphysiologically based pharmacokinetic (semi-PBPK) modeling approach. Preclinical and clinical data generated during the development of pafuramidine, a prodrug of the active metabolite, furamidine, were used. A whole-body semi-PBPK model for rats was developed based on a whole-liver PBPK model using rat isolated perfused liver data. A whole-body semi-PBPK model for humans was developed on the basis of the whole-body rat model. Scaling factors were calculated using metabolic and transport clearance data generated from rat and human sandwich-cultured hepatocytes. Both whole-body models described pafuramidine and furamidine disposition in plasma and predicted furamidine tissue (liver and kidney) exposure and excretion profiles (biliary and renal). The whole-body models predicted that the intestine contributes significantly (30-40%) to presystemic furamidine formation in both rats and humans. The predicted terminal elimination half-life of furamidine in plasma was 3- to 4-fold longer than that of pafuramidine in rats (170 versus 47 h) and humans (64 versus 19 h). The dose-plasma/tissue exposure relationship for the prodrug/active metabolite pair was determined using the whole-body models. The human model proposed a dose regimen of pafuramidine (40 mg once daily) based on a predefined efficacy-safety index. A similar approach could be used to guide dose-ranging studies in humans for next-in-class compounds.