Study of Rituximab Plus Pembrolizumab (MK-3475) in Subjects With Relapsed Follicular Lymphoma

Inclusion Criteria:

1. For cohort 1: Male or female subjects with histologic proof of follicular lymphoma
grade 1, 2, or 3a relapsing after at least one prior systemic therapy that included
rituximab (or other monoclonal CD20 antibody). Patients should have documented
rituximab-sensitive disease defined as a documented complete or partial response
lasting at least 6 months after the last rituximab containing.

2. For cohort 2: Male or female subjects with histologic proof of follicular lymphoma
grade 1, 2, or 3a relapsing after at least two prior systemic therapies, which must
include CAR T cell therapy or histologic proof of DLBCL relapsing after at least two
prior systemic therapies, which must include CAR T cell therapy.

3. Either the subject or his/her legally authorized representative be willing and able to
provide written informed consent for the trial.

4. Be >/= 18 years of age on day of signing informed consent.

5. Have measurable disease (>/= 1.5 cm in the longest diameter for nodal or extranodal
disease).

6. Have a performance status of 0 or 1 on the Eastern Cooperative Oncology Group (ECOG)
Performance Scale.

7. Demonstrate adequate organ function as defined below, all screening labs should be
performed within 28 days of treatment initiation. Hematological: Absolute neutrophil
count (ANC) >/=1.0 × 10^9/L; Platelets >/=50 × 10^9/L; Hemoglobin >/= 8.0 g/dL; Serum
creatinine OR Measured or calculated creatinine clearance (GFR can also be used in
place of creatinine or CrCl) (Creatinine clearance will be calculated per
institutional standard.) /=60 mL/min GFR or
CrCl for subjects with creatinine levels > 1.5 × institutional ULN; Hepatic: Serum
total bilirubin bilirubin levels > 1.5 ULN;

8. #6 cont...aspartate aminotransferase (AST)/serum glutamic oxaloacetic transaminase
(SGOT) and alanine aminotransferase (ALT)/ serum glutamic pyruvic transaminase (SGPT)
International Normalized Ratio (INR) or Prothrombin Time (PT) subject is receiving anticoagulant therapy as long as PT or Partial Thromboplastin
Time (PTT) is within therapeutic range of intended use of anticoagulants; Activated
Partial Thromboplastin Time (aPTT) anticoagulant therapy as long as PT or PTT is within therapeutic range of intended use
of anticoagulants

9. Female subject of childbearing potential should have a negative urine or serum
pregnancy test within 72 hours prior to receiving the first dose of study medication.
If the urine test is positive or cannot be confirmed as negative, a serum pregnancy
test will be required.

10. Female subjects of childbearing potential should be willing to use 2 methods of birth
control or be surgically sterile, or abstain from heterosexual activity for the course
of the study through 120 days after the last dose of study medication. Female subjects
of childbearing potential are those who have not been surgically sterilized or have
not been free from menses for > 1 year. a. Females of reproductive potential enrolled
in the lenalidomide cohort must adhere to the scheduled pregnancy testing as required
in the Revlimid REMS® program.

11. Male subjects should agree to use two methods of contraception starting with the first
dose of study therapy through 120 days after the last dose of study therapy.

12. All study participants enrolled in the lenalidomide containing cohort (cohort 2) must
be registered into the mandatory Revlimid REMS® program, and be willing and able to
comply with the requirements of the REMS® program.

Exclusion Criteria:

1. Is currently participating and receiving study therapy or has participated in a study
of an investigational agent and received study drug or using an investigation device
within 4 weeks of the first dose of treatment.

2. Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy or any
other form of immunosuppressive therapy within 7 days prior to the first dose of trial
treatment.

3. Has had a prior monoclonal antibody within 4 weeks prior to study Day 1 or who has not
recovered (i.e., than 4 weeks earlier.

4. Has had prior chemotherapy, targeted small molecule therapy, or radiation therapy
within 2 weeks prior to study Day 1 or who has not recovered (i.e., baseline) from AEs due to a previously administered agent. - Note: Subjects with Grade 2 neuropathy are an exception to this criterion and may qualify for the study. -
Note: If subject received major surgery, they must have recovered adequately from the
toxicity and/or complications from the intervention prior to starting therapy.

5. Has a known additional malignancy that is progressing and requires active treatment.
Exceptions include basal cell carcinoma of the skin, squamous cell carcinoma of the
skin, or in situ cervical cancer that has undergone potentially curative therapy.

6. Has known active central nervous system (CNS) lymphoma and/or lymphomatous meningitis.
Subjects with previously treated CNS lymphoma and/or lymphomatous meningitis may
participate provided they are stable (without evidence of progression by imaging for
at least four weeks prior to the first dose of trial treatment and any neurologic
symptoms have returned to baseline), have no evidence of new or enlarging brain
metastases, and are not using steroids for at least 7 days prior to trial treatment.

7. No active autoimmune disease that has required systemic treatment in past 2 years
(i.e. with use of disease modifying agents, corticosteroids or immunosuppressive
drugs). Replacement therapy (eg., thyroxine, insulin, or physiologic corticosteroid
replacement therapy for adrenal or pituitary insufficiency, etc.) is not considered a
form of systemic treatment. Subjects with vitiligo or resolved childhood asthma/atopy
would be an exception to this rule. Subjects that require intermittent use of
bronchodilators, local steroid injections or inhaled or topical steroids would not be
excluded from the study. Subjects with hypothyroidism stable on hormone replacement or
Sjorgen's syndrome will not be excluded from the study.

8. Has evidence of interstitial lung disease or active, non-infectious pneumonitis that
required steroids or current pneumonitis.

9. Has an active infection requiring systemic therapy.

10. Has a history or current evidence of any condition, therapy, or laboratory abnormality
that might confound the results of the trial, interfere with the subject's
participation for the full duration of the trial, or is not in the best interest of
the subject to participate, in the opinion of the treating investigator.

11. Has known psychiatric or substance abuse disorders that would interfere with
cooperation with the requirements of the trial.

12. Is pregnant or breastfeeding, or expecting to conceive or father children within the
projected duration of the trial, starting with the pre-screening or screening visit
through 120 days after the last dose of trial treatment.

13. .Has received prior therapy with an anti-PD-1, anti-PD-L1, anti-PD-L2, anti-CD137, or
anti-Cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) antibody (including
ipilimumab or any other antibody or drug specifically targeting T-cell co-stimulation
or checkpoint pathways).- Note: Subjects that received prior therapy with pidilizumab
are an exception to this criterion and may qualify for the study.

14. Has a known history of Human Immunodeficiency Virus (HIV) (HIV 1/2 antibodies).

15. Has known active Hepatitis B (e.g., HBsAg reactive) or Hepatitis C (e.g., HCV RNA
[qualitative] is detected).

16. Has received a live vaccine within 30 days prior to the first dose of trial treatment.