An Open-Label, Non-Randomized Study to Assess the Safety and Efficacy of Leniolisib in Japanese Patients With Activated Phosphoinositide 3-Kinase Delta Syndrome (APDS) Followed By an Open-Label Long-Term Extension.

For the treatment of activated phosphoinositide 3-kinase delta (PI3Kδ) syndrome (APDS).

This is a 2-part, open-label, non-randomized study to assess the safety and efficacy of leniolisib in Japanese patients with APDS. At least3 patients, aged 12 to 75 years (inclusive), will be enrolled. Patient eligibility will be assessed during a 7-week Screening Period (Day -50 to Day -1). This will be followed by a 12-week Treatment Period (Part 1), in which patients will be administered leniolisib doses ranging from 40 to 70 mg twice daily (BID) based on body weight (see dose regimen table below). A Part 1 clinical study report will be generated once the last patient completes the Day 85 Visit for Part 1. Patients who complete the Day 85 Visit will enter the Extension Period of the study (Part 2), in which patients will be administered leniolisib doses ranging from 40 to 70 mg BID (based on body weight) for 1 year or until marketing approval in Japan, whichever is longer. A 4-week Follow-up Period will occur after the last dose of study treatment is received.

It is anticipated that a total of 3 patients will be enrolled into the study.

Objectives:

Part 1:

Primary:

• To assess the safety and tolerability of leniolisib
• To assess the efficacy of leniolisib on lymphoproliferation (sum of product diameters [SPD] of index lymph node lesions) and immunophenotype normalization (percentage of naïve B cells out of total B cells)

Secondary:

• To assess the efficacy of leniolisib on lymphoproliferation (non-index lymph node lesions and spleen)
• To assess the pharmacokinetics (PK) of leniolisib in the Japanese population
• To assess the efficacy of leniolisib to modify health-related quality of life
• To assess the efficacy of leniolisib by the Patient's and Physician's Global Assessments
• To assess the frequency of infections, antibiotic use, and immunoglobulin (Ig) replacement therapy and assessment of impact on other disease-related outcomes (e.g., cytopenia, colitis, and lung function)
• To assess biomarkers reflecting the efficacy of leniolisib to reduce systemic inflammatory components of the disease
• To assess the treatment benefit to individual patients

Part 2:

Primary:

- To assess the long-term safety and tolerability of leniolisib

Secondary:

• To assess the long-term efficacy of leniolisib to modify health-related quality of life
• To assess the long-term efficacy of leniolisib on lymphoproliferation (non-index lymph node lesions and spleen)

Inclusion Criteria:

• Patient is Japanese.
• Patient is male or female and 12 to 75 years of age (inclusive) at the time of the first study procedure.
• Patient weighs ≥35 kg at baseline.
• Patient has a PI3Kδ genetic mutation of either the PIK3CD (APDS1) or PIK3R1 (APDS2) gene.
• Patient has at least 1 measurable nodal lesion on computed tomography (CT) or magnetic resonance imaging (MRI) scan within 6 months of Screening.
• Patient has nodal and/or extranodal lymphoproliferation and clinical findings and manifestations consistent with APDS (e.g., a history of repeated oto-sino-pulmonary infections and/or organ dysfunction consistent with APDS).
• At Screening, patient has sitting vital signs (with patient rested for at least 3 minutes) within the following ranges:
• Systolic blood pressure, 90-160 mm Hg
• Diastolic blood pressure, 50-95 mm Hg
• Pulse rate, 40-100 bpm; up to 110 bpm in adolescents

Exclusion Criteria:

- Patient has previous or concurrent use of immunosuppressive medication such as the following:

1. A mammalian target of rapamycin inhibitor (e.g., sirolimus, rapamycin, or everolimus) or a PI3Kδ inhibitor (selective or non-selective phosphoinositide 3-kinase inhibitors) within 6 weeks prior to first dose.

   - Short-term use for up to a total of 5 days is allowed but only up to 1 month prior to enrollment in the study.

2. B-cell depleters (e.g., rituximab) within 6 months prior to first dose of study treatment.

   - If patient has received prior treatment with a B-cell depleter, absolute B lymphocyte counts in the blood must have regained normal values.

3. Belimumab or cyclophosphamide within 6 months prior to first dose of study treatment.

4. Cyclosporine A, mycophenolate, 6-mercaptopurine, azathioprine, or methotrexate within 3 months prior to first dose of study treatment.

5. Glucocorticoids above 25 mg prednisone or equivalent per day within 2 weeks prior to first dose of study treatment.

6. Other immunosuppressive medications where effects are expected to persist at start of dosing of study treatment.

   • Patient has had a hematopoietic stem-cell transplant, hematopoietic cell transplant, or bone marrow transplant.
   • Patient is currently using a medication known to be a strong inhibitor or moderate or strong inducer of isoenzyme cytochrome P450 (CYP)3A if treatment cannot be discontinued or switched to a different medication prior to starting study treatment.
   • Patient is currently using medications that are metabolized by isoenzyme CYP1A2 and have a narrow therapeutic index (drugs whose exposure response indicates that increases in their exposure levels by the concomitant use of potent inhibitors may lead to serious safety concerns [e.g., Torsades de Pointes]).
   • Patient had been administered a live vaccine (this includes any attenuated live vaccines) starting from 6 weeks before the anticipated first dose of study treatment, during the treatment period, and up to 7 days after the last dose of leniolisib.
   • Patient is a pregnant or nursing (lactating) woman, where pregnancy is defined as the state of a female after conception and until the termination of gestation, confirmed by a positive human chorionic gonadotropin laboratory test.
   • Patient is a woman of child-bearing potential, defined as a woman physiologically capable of becoming pregnant, unless she is using highly effective methods of contraception during dosing of study treatment and for 30 days after the last study procedure.