Trial Outcomes & Findings for A Study of Pembrolizumab (MK-3475) in Participants With Relapsed or Refractory Primary Mediastinal Large B-cell Lymphoma (rrPMBCL) (MK-3475-A33/KEYNOTE-A33) (NCT NCT04317066)

NCT ID: NCT04317066

Last Updated: 2025-04-06

Results Overview

ORR is defined as the percentage of participants with response (complete response, CR or partial response, PR) according to the International Working Group (IWG) Response Assessment Criteria for Malignant Lymphoma per Cheson 2007. CR is the disappearance of all evidence of disease. PR is ≥ 50% decrease in the sum of product diameters (SPD) of the six largest dominant nodes or nodal masses, ≥ 50% decrease in SPD of splenic and hepatic nodules, no increase in the size of the other nodes, liver, or spleen plus no measurable disease in other organs and no new sites of disease. Per protocol, the percentage of participants who experienced a CR or PR as assessed by independent central review were reported.

• Recruitment status: COMPLETED
• Study phase: PHASE1
• Target enrollment: 7 participants
• Primary outcome timeframe: Up to approximately 24 months
• Results posted on: 2025-04-06

Participant Flow

All allocated participants.

Participant milestones

Measure	Pembrolizumab in Participants With rrPMBCL Participants with relapsed or refractory primary mediastinal large B-cell lymphoma (rrPMBCL) received Pembrolizumab 200 mg by Intravenous (IV) infusion on day 1 of each 3-week cycle for up to 35 cycles (approximately 2 years).
Overall Study STARTED	7
Overall Study COMPLETED	0
Overall Study NOT COMPLETED	7

Reasons for withdrawal

Measure	Pembrolizumab in Participants With rrPMBCL Participants with relapsed or refractory primary mediastinal large B-cell lymphoma (rrPMBCL) received Pembrolizumab 200 mg by Intravenous (IV) infusion on day 1 of each 3-week cycle for up to 35 cycles (approximately 2 years).
Overall Study Sponsor decision	5
Overall Study Death	2

Baseline Characteristics

A Study of Pembrolizumab (MK-3475) in Participants With Relapsed or Refractory Primary Mediastinal Large B-cell Lymphoma (rrPMBCL) (MK-3475-A33/KEYNOTE-A33)

Baseline characteristics by cohort

Measure	Pembrolizumab in Participants With rrPMBCL n=7 Participants Participants with relapsed or refractory primary mediastinal large B-cell lymphoma (rrPMBCL) received Pembrolizumab 200 mg by Intravenous (IV) infusion on day 1 of each 3-week cycle for up to 35 cycles (approximately 2 years).
Age, Continuous	32.3 Years STANDARD_DEVIATION 6.7 • n=5 Participants
Sex: Female, Male Female	6 Participants n=5 Participants
Sex: Female, Male Male	1 Participants n=5 Participants
Ethnicity (NIH/OMB) Hispanic or Latino	0 Participants n=5 Participants
Ethnicity (NIH/OMB) Not Hispanic or Latino	7 Participants n=5 Participants
Ethnicity (NIH/OMB) Unknown or Not Reported	0 Participants n=5 Participants
Race (NIH/OMB) American Indian or Alaska Native	0 Participants n=5 Participants
Race (NIH/OMB) Asian	7 Participants n=5 Participants
Race (NIH/OMB) Native Hawaiian or Other Pacific Islander	0 Participants n=5 Participants
Race (NIH/OMB) Black or African American	0 Participants n=5 Participants
Race (NIH/OMB) White	0 Participants n=5 Participants
Race (NIH/OMB) More than one race	0 Participants n=5 Participants
Race (NIH/OMB) Unknown or Not Reported	0 Participants n=5 Participants

PRIMARY outcome

Timeframe: Up to approximately 24 months

Population: The analysis population consisted of all participants who received at least 1 dose of study treatment.

ORR is defined as the percentage of participants with response (complete response, CR or partial response, PR) according to the International Working Group (IWG) Response Assessment Criteria for Malignant Lymphoma per Cheson 2007. CR is the disappearance of all evidence of disease. PR is ≥ 50% decrease in the sum of product diameters (SPD) of the six largest dominant nodes or nodal masses, ≥ 50% decrease in SPD of splenic and hepatic nodules, no increase in the size of the other nodes, liver, or spleen plus no measurable disease in other organs and no new sites of disease. Per protocol, the percentage of participants who experienced a CR or PR as assessed by independent central review were reported.

Outcome measures

Measure	Pembrolizumab in Participants With rrPMBCL n=7 Participants Participants with relapsed or refractory primary mediastinal large B-cell lymphoma (rrPMBCL) received Pembrolizumab 200 mg by Intravenous (IV) infusion on day 1 of each 3-week cycle for up to 35 cycles (approximately 2 years).
Objective Response Rate (ORR) Using International Working Group (IWG) Revised Response Criteria for Malignant Lymphoma as Assessed by Independent Central Review	42.9 Percentage of Participants Interval 9.9 to 81.6

PRIMARY outcome

Timeframe: Up to approximately 27 months

Population: The analysis population consisted of all participants who received at least 1 dose of study treatment.

An adverse event (AE) was defined as any unfavorable and unintended sign including an abnormal laboratory finding, symptom or disease associated with the use of a medical treatment or procedure, regardless of whether it is considered related to the medical treatment or procedure, which occurs during the course of the study. Per protocol, the number of participants who experienced at least one AE were reported.

Outcome measures

Measure	Pembrolizumab in Participants With rrPMBCL n=7 Participants Participants with relapsed or refractory primary mediastinal large B-cell lymphoma (rrPMBCL) received Pembrolizumab 200 mg by Intravenous (IV) infusion on day 1 of each 3-week cycle for up to 35 cycles (approximately 2 years).
Number of Participants Who Experienced at Least One Adverse Event (AE)	7 Participants

PRIMARY outcome

Timeframe: Up to approximately 24 months

Population: The analysis population consisted of all participants who received at least 1 dose of study treatment.

An AE was defined as any unfavorable and unintended sign including an abnormal laboratory finding, symptom or disease associated with the use of a medical treatment or procedure, regardless of whether it is considered related to the medical treatment or procedure, which occurs during the course of the study. Per protocol, the number of participants who discontinued study treatment due to an AE were reported.

Outcome measures

Measure	Pembrolizumab in Participants With rrPMBCL n=7 Participants Participants with relapsed or refractory primary mediastinal large B-cell lymphoma (rrPMBCL) received Pembrolizumab 200 mg by Intravenous (IV) infusion on day 1 of each 3-week cycle for up to 35 cycles (approximately 2 years).
Number of Participants Who Discontinued Study Treatment Due to an Adverse Event (AE)	0 Participants

SECONDARY outcome

Timeframe: Up to approximately 24 months

Population: The analysis population consisted of all participants who received at least 1 dose of study treatment.

ORR is defined as the percentage of participants with response (complete response, CR or partial response, PR) according to the International Working Group (IWG) Response Assessment Criteria for Malignant Lymphoma per Cheson 2007. CR is the disappearance of all evidence of disease. PR is ≥ 50% decrease in the sum of product diameters (SPD) of the six largest dominant nodes or nodal masses, ≥ 50% decrease in SPD of splenic and hepatic nodules, no increase in the size of the other nodes, liver, or spleen plus no measurable disease in other organs and no new sites of disease. Per protocol, the percentage of participants who experienced a CR or PR as assessed by investigator review were reported.

Outcome measures

Measure	Pembrolizumab in Participants With rrPMBCL n=7 Participants Participants with relapsed or refractory primary mediastinal large B-cell lymphoma (rrPMBCL) received Pembrolizumab 200 mg by Intravenous (IV) infusion on day 1 of each 3-week cycle for up to 35 cycles (approximately 2 years).
Objective Response Rate (ORR) Using International Working Group (IWG) Revised Response Criteria for Malignant Lymphoma as Assessed by Investigator	57.1 Percentage of Participants Interval 18.4 to 90.1

SECONDARY outcome

Timeframe: Up to approximately 24 months

Population: The analysis population consisted of all participants who received at least 1 dose of study treatment.

The DCR was defined as the percentage of participants in the analysis population who have achieved a CR, PR or stable disease (SD) response prior to PD according to the International Working Group (IWG) Response Assessment Criteria for Malignant Lymphoma per Cheson 2007. CR is the disappearance of all evidence of disease and PR is the regression of measurable disease and no new sites of disease. SD is the failure to attain CR/PR or PD. PD is the appearance any new lesion or increase by ≥ 50% of previously involved site from nadir. Per protocol, the percentage of participants who experienced a CR, a PR, or SD as assessed by independent central review were reported.

Outcome measures

Measure	Pembrolizumab in Participants With rrPMBCL n=7 Participants Participants with relapsed or refractory primary mediastinal large B-cell lymphoma (rrPMBCL) received Pembrolizumab 200 mg by Intravenous (IV) infusion on day 1 of each 3-week cycle for up to 35 cycles (approximately 2 years).
Disease Control Rate (DCR) Using International Working Group (IWG) Revised Response Criteria for Malignant Lymphoma as Assessed by Independent Central Review	57.1 Percentage of Participants Interval 18.4 to 90.1

SECONDARY outcome

Timeframe: Up to approximately 24 months

Population: The analysis population consisted of all participants who received at least 1 dose of study treatment.

The DCR was defined as the percentage of participants in the analysis population who have achieved a CR, PR or stable disease (SD) response prior to PD according to the International Working Group (IWG) Response Assessment Criteria for Malignant Lymphoma per Cheson 2007. CR is the disappearance of all evidence of disease and PR is the regression of measurable disease and no new sites of disease. SD is the failure to attain CR/PR or PD. PD is the appearance any new lesion or increase by ≥ 50% of previously involved site from nadir. Per protocol, the percentage of participants who experienced a CR, a PR, or SD as assessed by investigator review were reported.

Outcome measures

Measure	Pembrolizumab in Participants With rrPMBCL n=7 Participants Participants with relapsed or refractory primary mediastinal large B-cell lymphoma (rrPMBCL) received Pembrolizumab 200 mg by Intravenous (IV) infusion on day 1 of each 3-week cycle for up to 35 cycles (approximately 2 years).
Disease Control Rate (DCR) Using International Working Group (IWG) Revised Response Criteria for Malignant Lymphoma as Assessed by Investigator	71.4 Percentage of Participants Interval 29.0 to 96.3

Adverse Events

Pembrolizumab in Participants With rrPMBCL

Serious events: 1 serious events

Other events: 7 other events

Deaths: 2 deaths

Serious adverse events

Measure	Pembrolizumab in Participants With rrPMBCL n=7 participants at risk Participants with relapsed or refractory primary mediastinal large B-cell lymphoma (rrPMBCL) received Pembrolizumab 200 mg by Intravenous (IV) infusion on day 1 of each 3-week cycle for up to 35 cycles (approximately 2 years).
Endocrine disorders Adrenal insufficiency	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.

Other adverse events

Measure	Pembrolizumab in Participants With rrPMBCL n=7 participants at risk Participants with relapsed or refractory primary mediastinal large B-cell lymphoma (rrPMBCL) received Pembrolizumab 200 mg by Intravenous (IV) infusion on day 1 of each 3-week cycle for up to 35 cycles (approximately 2 years).
Blood and lymphatic system disorders Febrile neutropenia	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Blood and lymphatic system disorders Neutropenia	42.9% 3/7 • Number of events 3 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Abdominal pain	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Constipation	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Diarrhoea	28.6% 2/7 • Number of events 5 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Dry mouth	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Gastrointestinal disorders Haemorrhoids	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
General disorders Malaise	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
General disorders Pyrexia	42.9% 3/7 • Number of events 3 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Immune system disorders Hypersensitivity	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Conjunctivitis	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Herpes zoster	28.6% 2/7 • Number of events 2 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Paronychia	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Infections and infestations Upper respiratory tract infection	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Investigations Alanine aminotransferase increased	28.6% 2/7 • Number of events 3 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Investigations Aspartate aminotransferase increased	28.6% 2/7 • Number of events 3 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Metabolism and nutrition disorders Decreased appetite	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Nervous system disorders Headache	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Nervous system disorders Peripheral sensory neuropathy	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Psychiatric disorders Insomnia	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Respiratory, thoracic and mediastinal disorders Cough	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Skin and subcutaneous tissue disorders Dry skin	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Skin and subcutaneous tissue disorders Erythema	14.3% 1/7 • Number of events 1 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.
Skin and subcutaneous tissue disorders Urticaria	28.6% 2/7 • Number of events 2 • Up to approximately 27 months All-Cause Mortality, serious and non-serious adverse events (AEs) were reported on all allocated participants who received at least 1 dose of study treatment.

Additional Information

Senior Vice President, Global Clinical Development

Merck Sharp & Dohme LLC

Phone: 1-800-672-6372

Email: ClinicalTrialsDisclosure@msd.com

Results disclosure agreements

• Principal investigator is a sponsor employee The sponsor must have the opportunity to review all manuscripts or abstracts before submission. Any information identified by the sponsor as confidential must be deleted prior to submission.
• Publication restrictions are in place

Restriction type: OTHER