Inclusion Criteria:

          1. Age ≥ 18 years of age

          2. Diagnosis of one of the following histologic subtypes of PTCL,
             pathologically-confirmed, as defined by the World Health Organization:

               1. Peripheral T-cell lymphoma-not otherwise specified (PTCL-NOS);

               2. Angioimmunoblastic T-cell lymphomas (AITL);

               3. Anaplastic large cell lymphoma (ALCL); or

               4. Natural-killer/T-cell lymphoma (NKTL)

          3. Received at least 2 cycles of one prior regimen administered with curative intent and
             one of the following:

               1. failed to achieve at least a partial response after 2 or more cycles;

               2. failed to achieve a complete response after 6 or more cycles; and/or

               3. progressed after an initial response

          4. For patients with CD30+ ALCL, failed or are ineligible or intolerant to brentuximab
             vedotin

          5. Measurable disease as defined by IWG for PTCL, i.e., at least 1 measurable disease
             lesion > 1.5 cm in at least one dimension by 18FDG-PET-CT, MRI, or diagnostic CT

        Exclusion Criteria:

          1. Clinical evidence of transformation to a more aggressive subtype of lymphoma

          2. Received prior treatment with a phosphoinositide-3-kinase (PI3K) inhibitor

          3. Known central nervous system involvement by PTCL

          4. Ongoing treatment with chronic immunosuppressants (e.g., cyclosporine) or systemic
             steroids > 20 mg of prednisone (or equivalent) once daily (QD)

          5. Ongoing treatment for systemic bacterial, fungal, or viral infection at Screening