Pembrolizumab has been approved by the FDA for the treatment of adult and pediatric patients with refractory classical Hodgkin lymphoma (cHL), or who have relapsed after three or more prior lines of therapy. Under the FDA's accelerated approval regulations, this indication is approved based on tumor response rate and durability of response. Continued approval for this indication may be contingent upon verification and description of clinical benefit in the confirmatory trials.
In refractory or relapsed cHL, pembrolizumab is approved for use in adult patients at a fixed dose of 200 mg and in pediatric patients at a dose of 2 mg/kg (up to a maximum of 200 mg). Pembrolizumab is administered intravenously every 3 weeks until disease progression or unacceptable toxicity, or up to 24 months in patients without disease progression.
The accelerated FDA approval was based on data in 210 patients with relapsed or refractory cHL enrolled in the multicenter, nonrandomized, open-label KEYNOTE-087 study.
Patients received pembrolizumab at a dose of 200 mg every 3 weeks until unacceptable toxicity or documented disease progression, or for up to 24 months in patients who did not progress. The major efficacy outcome measures (ORR, CRR, and duration of response) were assessed by blinded independent central review according to the 2007 revised International Working Group criteria. Fifty-eight percent of patients were refractory to the last prior therapy, including 35 percent with primary refractory disease and 14 percent whose disease was chemo-refractory to all prior regimens. Additionally, 61 percent of patients had undergone prior auto-HSCT, 17 percent had no prior brentuximab use, and 36 percent had prior radiation therapy.
Efficacy analysis showed an ORR of 69 percent (95% CI: 62, 75) with a CRR of 22 percent and a PRR of 47 percent. The median follow-up time was 9.4 months. Among the 145 responding patients, the median duration of response was 11.1 months (range 0.0+ to 11.1 months).
Pembrolizumab was discontinued due to adverse reactions in 5 percent of 210 patients with cHL and treatment was interrupted due to adverse reactions in 26 percent of patients. Fifteen percent of patients had an adverse reaction requiring systemic corticosteroid therapy. Serious adverse reactions occurred in 16 percent of patients. The most frequent serious adverse reactions (≥1%) included pneumonia, pneumonitis, pyrexia, dyspnea, GVHD, and herpes zoster. Two patients died from causes other than disease progression; one from GVHD after subsequent allogeneic HSCT and one from septic shock. The most common adverse reactions (occurring in ≥20% of patients) were fatigue (26%), pyrexia (24%), cough (24%), musculoskeletal pain (21%), diarrhea (20%), and rash (20%).
There is limited experience in pediatric patients. Efficacy for pediatric patients was extrapolated from the results in the adult cHL population. In a study of 40 pediatric patients with advanced melanoma, PD-L1-positive advanced, relapsed, or refractory solid tumors or lymphoma, patients were treated with pembrolizumab for a median of 43 days (range 1-414 days), with 24 patients (60%) receiving treatment for 42 days or more. The safety profile in pediatric patients was similar to that seen in adults treated with pembrolizumab. Toxicities that occurred at a higher rate (≥15% difference) in these patients when compared to adults under 65 years of age were fatigue (45%), vomiting (38%), abdominal pain (28%), hypertransaminasemia (28%), and hyponatremia (18%).