A Study of ME-401 in Subjects With CLL/SLL, FL, and B-cell Non Hodgkin's Lymphoma

This is a two-arm, Phase 1b, open-label, dose escalation study of ME-401 alone and an
open-label study of ME-401 in combination with rituximab in patients with relapsed/refractory
B-cell malignancies. The two arms of the study will be conducted in parallel, with subject
allocation to ME-401 alone or ME-401 plus rituximab based on disease type and availability of
an open enrollment slot.

Inclusion Criteria MEI-401 Alone:

- Diagnosis of relapsed/refractory CLL and/or relapsed/refractory SLL or FL

- No prior therapy with PI3Kd inhibitors

- No prior therapy with Bruton tyrosine kinase (BTK) inhibitors unless the subject was
intolerant of BTK therapy

- Subject must have failed at least 1 prior systemic therapy

- QT-interval corrected according to Fridericia's formula (QTcF) ≤ 450 milliseconds (ms)

- Left ventricular ejection fraction >50%

- For subjects, except those with CLL, must have at least one bi-dimensionally
measurable nodal lesion >1.5 cm, as defined by Lugano Classification

- Willingness to participate in collection of pharmacokinetic samples

- A negative serum pregnancy test within 14 days of study Day 0, for females of
childbearing potential

Inclusion Criteria ME-401 in Combination with Rituximab

- Diagnosis of relapsed/refractory CLL SLL or FL, MZL, DLBCL and high-grade B-cell
lymphoma. Subjects must meet the following criteria for relapsed or refractory
disease:

1. Relapsed disease: a subject who previously achieved a CR or PR, but demonstrated
disease progression after a response duration of >6 months

2. Refractory disease: a subject who demonstrated disease progression within 6
months of most recent therapy

- No prior therapy with PI3Kδ inhibitors

- No prior therapy with Bruton tyrosine kinase (BTK) inhibitors unless the subject was
intolerant of BTK therapy

- Subjects with CLL, SLL, FL, and MZL must have a failure of at least 1 prior systemic
therapy and be considered by the investigator a candidate for therapy with a
rituximab-based regimen; subjects with DLBCL and high-grade B-cell lymphoma must have
a failure of at least 2 prior therapies.

- QT-interval corrected according to Fridericia's formula (QTcF) ≤450 milliseconds (ms)

- Left ventricular ejection fraction >50%

- For subjects, except those with CLL, must have at least one bi-dimensionally
measurable nodal lesion >1.5 cm, as defined by Lugano Classification

- Willingness to participate in collection of pharmacokinetic samples

- A negative serum pregnancy test within 14 days of study Day 0 for females of
childbearing potential

Exclusion Criteria:

- Known histological transformation from CLL to an aggressive lymphoma

- Uncontrolled autoimmune hemolytic anemia or immune thrombocytopenia

- Subjects who have tested positive for hepatitis B surface antigen and/or hepatitis B
core antibody

- Positive for hepatitis C virus antibody (HCV Ab) or human immunodeficiency virus (HIV)
antibody

- Ongoing drug-induced pneumonitis

- History of clinically significant cardiovascular abnormalities