The purpose of this study is to evaluate the safety, tolerability, and pharmacokinetics of ME-401 in the treatment of Japanese participants with Relapsed or Refractory indolent B-Cell Non-Hodgkin's Lymphoma and to continue administraion of ME-401 to patients with relapsed or refractory B-cell NHL with collecting safety information

Inclusion Criteria:

[Phase 1 study (DLT evaluation)]

• Patients aged 20 years or older at the submission of the written informed consent form
• Patients with relapsed or refractory B-cell NHL
• Patients who have not undergone phosphatidylinositol 3-kinase inhibitor (PI3K) to date.
• Patients who have undergone Bruton's tyrosine kinase (BTK) inhibitors and have had no exacerbation during the use of BTK inhibitors.
• Patients with ECOG PS 0 or 1.

Exclusion Criteria:

[Phase 1 study (DLT evaluation)]

• Patients who underwent any major surgical treatment within 4 weeks prior to the initiation of the investigational product.
• Patients with poorly controlled diseases. The followings are the examples but the diseases will not be limited to those.
• Patients in whom any of HBV antigen/antibody, HCV antibody, HIV antibody or HTLV-1 antibody will be positive at screening test.
• Patients with active interstitial lung disease or a history thereof.
• Patients who have received the investigational products other than ME-401, systemic chemotherapy or radiotherapy within 4 weeks prior to the initiation of ME-401.