Merck’s KEYTRUDA Shines in R/R cHL and R/R PMBCL, Paving the Way to Promising Treatment Options


KEYTRUDA (pembrolizumab) is a monoclonal antibody that falls into the category of drugs that target the programmed death receptor-1 (PD-1) or programmed death ligand 1 (PD-L1). By binding to PD-1 or PD-L1, KEYTRUDA blocks the PD-1/PD-L1 pathway, thereby releasing the inhibition on the immune response. This mechanism has the potential to disrupt peripheral tolerance and trigger immune-mediated adverse reactions. These adverse reactions can occur in various organs or tissues, affecting multiple body systems simultaneously. It is important to note that these reactions, which can be severe or even fatal, may manifest at any time during treatment or following the discontinuation of KEYTRUDA.

KEYTRUDA is approved for the treatment of refractory PMBCL in both adult and pediatric patients. It is also indicated for patients who have experienced relapse after receiving two or more prior lines of therapy. However, it is important to note that KEYTRUDA is not recommended for patients with PMBCL who require immediate cytoreductive therapy.

Pembrolizumab has shown impressive effectiveness and manageable safety in R/R cHL and R/R PMBCL, leading to FDA approval. The recent accelerated approval of pembrolizumab 400 mg Q6W across all indications was based on solid tumor trial data. A global Phase II trial is currently assessing the efficacy and safety of pembrolizumab 400 mg Q6W in relapsed/refractory cHL and PMBCL. The company is presenting the first-ever data from 66 patients with a follow-up period of approximately 9 months.

In patients with R/R cHL, the median follow-up was 8.9 months, while in those with R/R PMBCL, it was 10.6 months. The ORR for R/R cHL was 65%, with 33.3% achieving complete response (CR) and 31.7% achieving partial response (PR). For R/R PMBCL, the ORR was 50%, with 33.3% CR and 16.7% PR. Among R/R cHL patients, 40% experienced drug-related adverse events (AEs), while the percentage was 33.3% in R/R PMBCL. Grade ≥3 drug-related AEs occurred in 5% of R/R cHL patients and 16.7% of R/R PMBCL patients. Immune-mediated AEs were observed in 21.7% of R/R cHL patients and 16.7% of R/R PMBCL patients, with grade ≥3 immune-mediated AEs seen in 3.3% of R/R cHL patients. These findings highlight the clinical outcomes and safety profile of the treatment in both R/R cHL and R/R PMBCL patient populations.

Table 1: Efficacy results


N = 60

N = 6

ORR (%)


3 (50.0) [11.8, 88.2]



2 (33.3)



1 (16.7)

Median DOR months



9-months DOR rate, %



Median OS months



12-months OS rate, %



Median PFS months



12-months PFS rate, %



Note: NR = Not reached

KOL insights

“The results offer strong support for the effectiveness and tolerability of pembrolizumab in relapsed/refractory cHL and PMBCL, reaffirming its significance as a valuable therapeutic choice for patients grappling with these difficult cancers.” –Expert Opinion.

Conclusion: After a follow-up period of around 9 months, the administration of pembrolizumab at a dose of 400 mg Q6W shows strong effectiveness in patients with R/R cHL and R/R PMBCL. The ORR is comparable to that seen with pembrolizumab at a dose of 200 mg Q3W in these specific lymphoma types. Importantly, the use of pembrolizumab at 400 mg Q6W does not raise any new safety concerns, thereby supporting the adoption of this dosing schedule in hematologic indications. These findings provide compelling evidence for the efficacy and safety of pembrolizumab in R/R cHL and R/R PMBCL, reinforcing its role as a valuable treatment option for patients with these challenging malignancies