ZYNYZ Solution for injection Ref.[107364] Active ingredients: Retifanlimab

The exposure-response relationship and time course of pharmacodynamic response for safety and effectiveness of retifanlimab-dlwr have not been fully characterized.

The pharmacokinetics of retifanlimab-dlwr were evaluated in patients with various solid tumors, including patients with MCC. Retifanlimab-dlwr exposures (maximum concentration [C_max] and area under the curve [AUC]) increased proportionally over a dosage range from 375 mg to 750 mg (0.75- to 1.5-fold of the approved recommended dose).

Following administration of retifanlimab-dlwr at 500 mg every 4 weeks, steady-state concentrations were achieved at Cycle 6 (approximately 6 months) and systemic accumulation was 1.3-fold.

Distribution

The geometric mean volume of distribution at steady state for retifanlimab-dlwr is 6.0 L (coefficient of variation [CV]: 20%).

Elimination

The elimination half-life of retifanlimab-dlwr at steady state is 19 days (CV: 29%). Clearance of retifanlimab-dlwr after the first dose was 0.31 L/day (CV: 36%) and decreased over time by approximately 23%, resulting in a steady-state clearance of 0.24 L/day.

Specific Populations

The following factors have no clinically meaningful effect on the pharmacokinetics of retifanlimab-dlwr: age (18 to 94 years), sex, body weight (35 to 133 kg), race (White, Black, Asian), albumin level (21 to 54 g/L), Eastern Cooperative Oncology Group (ECOG) score (0 to 2), tumor burden (sum of the target lesion diameters: 10 to 360 mm), HIV status, renal function (estimated glomerular filtration rate ≥26 mL/min/1.73 m²), or mild hepatic impairment (total bilirubin less than or equal to the ULN and AST greater than ULN or total bilirubin greater than ULN and less than or equal to 1.5 times ULN and any AST). The pharmacokinetics of retifanlimab-dlwr have not been studied in patients with moderate or severe hepatic impairment.

No studies have been performed to assess the potential of retifanlimab-dlwr for carcinogenicity or genotoxicity.

In 1-month and 3-month repeat-dose toxicology studies in monkeys, there were no notable effects in the male and female reproductive organs; however, most animals in these studies were not sexually mature.

In animal models, inhibition of PD-L1/PD-1 signaling increased the severity of some infections and enhanced inflammatory responses. Mycobacterium tuberculosis–infected PD-1 knockout mice exhibit markedly decreased survival compared with wild-type controls, which correlated with increased bacterial proliferation and inflammatory responses in these animals. PD-1 blockade using a primate anti-PD-1 antibody was also shown to exacerbate M. tuberculosis infection in rhesus macaques. PD-L1 and PD-1 knockout mice and mice receiving PD-L1 blocking antibody have also shown decreased survival following infection with lymphocytic choriomeningitis virus.

The efficacy of ZYNYZ was evaluated in study POD1UM-201 (NCT03599713), an open-label, multiregional, single-arm study in 65 patients with metastatic or recurrent locally advanced MCC who had not received prior systemic therapy for their advanced disease. Patients with active autoimmune disease or a medical condition that required immunosuppression were ineligible. Patients who were HIV-positive, with an undetectable viral load, a CD4+ count ≥300 cells/microliter and receiving antiretroviral therapy were eligible.

Patients received ZYNYZ 500 mg intravenously every 4 weeks until disease progression, unacceptable toxicity, or up to 24 months. Tumor response assessments were performed every 8 weeks for the first year of therapy and 12 weeks thereafter.

The major efficacy outcomes were objective response rate (ORR) and duration of response (DOR) as assessed by an independent central review committee (IRC) according to Response Evaluation Criteria in Solid Tumors (RECIST) v1.1.

The median age of enrolled patients was 71 years (range: 44-90); 37% were ≥75 years; 65% of patients were male; 78% of patients were White, 20% were race unknown or not reported, 2% were Asian; 74% had an ECOG performance status of 0 and 26% had an ECOG performance status of 1; 98% were HIV-negative. Seventy-two percent of patients had prior surgery and 38% of patients had prior radiotherapy. Eighty-eight percent of patients had metastatic disease at baseline. Tumor samples were evaluated for Merkel cell polyomavirus (MCPyV): 71% were positive, 23% negative, 2% equivocal, and 5% missing.

Efficacy results are summarized in Table 4.

Table 4. Efficacy Results from Study POD1UM-201:

CI = confidence interval; DOR = duration of response; + denotes ongoing response.