Checkpoint inhibitors forge new treatment paradigm for metastatic bladder cancer

Last spring, the US Food and Drug Administration (FDA) granted accelerated approval to 3 different immune checkpoint inhibitors for the treatment of patients with metastatic urothelial carcinoma in the second-line setting, bringing the total number of approved members of this drug class for this indication to 5.

Avelumab and durvalumab, like atezolizumab, are monoclonal antibodies that target the programmed cell death protein ligand-1 (PD-L1) and prevent it from binding to and activating the programmed cell death protein-1 (PD-1) and CD80 receptors, which transmit inhibitory signals into T cells. In this way, it is hypothesized that their use reactivates the anti-tumor immune response conducted by tumor-infiltrating T cells. Both drugs were approved for the treatment of patients with locally advanced or metastatic urothelial carcinoma who are refractory to platinum-based chemotherapy, and the approvals provide additional treatment options for this group of patients who typically have poor prognosis.^1,2
 

Avelumab trial findings

The approval of avelumab was based on the urothelial cancer cohorts of the JAVELIN Solid Tumor trial, a phase 1, open-label, dose-escalation study.³ Patients aged 18 years and older, with an Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1 (range, 0-5; 0, fully active, and 5, dead), life expectancy of at least 3 months, and cytologically or histologically confirmed metastatic or locally advanced solid tumors were eligible.

Patients were excluded from the study if they had a history of or active central nervous system metastases, had other malignancies within the previous 5 years, had undergone organ transplant, had conditions requiring immune suppression, had active HIV or hepatitis B or C infection, or had autoimmune diseases other than type 1 diabetes, vitiligo, psoriasis, or thyroid disease that does not require immunosuppressive treatment.

Patients were also required to have adequate end organ function (white blood cell count, ≥3 x 10⁹ cells/L; absolute neutrophil count, ≥1.5 x 10⁹ cells/L; lymphocyte count, ≥0.5 x 10⁹ cells/L; platelet count, ≥100 x 10⁹ platelets/L; hemoglobin, ≥9 g/dL; total bilirubin concentration, ≤1.5 x upper limit of normal [ULN] range; aspartate- and alanine- aminotransferase (ALT/AST) concentrations, ≤2.5 x ULN); and estimated creatinine clearance, >50 mL/min.

A total of 242 patients were treated with a 10 mg/kg intravenous dose of avelumab every 2 weeks until disease progression or unacceptable toxicity. Before avelumab infusion, all patients received premedication with an antihistamine and acetaminophen.

The primary endpoint was objective response rate (ORR), which was 13.3% among 226 patients followed for at least 13 weeks, including 4% complete response (CR) rate, and 16.1% among 161 patients followed for at least 6 months, including 5.6% CR rate. The median time to response was 2 months and the median response duration had not been reached at the time of data cut-off. PD-L1 expression was evaluable in 84% of patients and there was no discernable variation in the response rates according to the levels of PD-L1 expression on the tumor.

The most common adverse events (AEs) that occurred in at least 20% of patients included fatigue, infusion-related reaction, musculoskeletal pain, nausea, decreased appetite, and urinary tract infection (UTI). Serious AEs occurred in 41% of patients and most commonly involved UTI, abdominal pain, musculoskeletal pain, creatinine increase/renal failure, dehydration, hematuria, intestinal obstruction, and pyrexia. Deaths owing to AEs occurred in 6% of patients and were related to pneumonitis, respiratory failure, sepsis/urosepsis, cerebrovascular accident, or gastrointestinal AEs.

Durvalumab approval

The agency’s approval of durvalumab rested on the results of an ongoing single-arm phase 1/2 trial (Study 1108).⁴ Eligibility criteria were the same as for the avelumab study. Patients were ineligible for the trial if they had received any immunotherapy within the previous 4 weeks, any monoclonal antibody within the previous 6 weeks, or had received concurrent chemotherapy, immunotherapy, biologic, or hormonal therapy.

Durvalumab was administered as an intravenous infusion at a dose of 10 mg/kg every 2 weeks, for up to 12 months or until disease progression or unacceptable toxicity. PD-L1 expression was evaluated by immunohistochemistry in tumor tissue obtained before treatment using the Ventana PD-L1 (SP263) assay (Ventana Medical Systems), which was approved by the FDA alongside durvalumab as a companion diagnostic. The first 20 patients were enrolled regardless of their PD-L1 expression, and the subsequent 43 patients were required to have PD-L1 expression of at least 5% of their tumor cells, but that requirement was removed at an interim analysis when objective responses occurred in patients with a PD-L1 expression of lessthan 5%.

In the most up-to-date analysis, published after FDA approval, a total of 191 patients had been treated. The ORR as assessed by blinded independent central review per RECIST-1.1, was 17.8%, including 7 CRs (3.7%). In patients with high PD-L1 expression, the ORR was 27.6%, compared with 5.1% in those with low or no PD-L1 expression. Responses were observed across all subgroups, including patients with a poor prognosis. The ORRs in patients with visceral and liver metastases were 15.3% and 7.3%, respectively. The median time to response was 1.41 months, and the median duration of response had not yet been reached.

The most common AEs experienced by patients treated with durvalumab included fatigue, musculoskeletal pain, constipation, decreased appetite, nausea, peripheral edema, and UTI. Serious treatment-related AEs occurred in 4.7% of patients, and treatment-related AEs leading to death occurred in 2 patients owing to autoimmune hepatitis and pneumonitis.