This is an open-label Phase I/II study, with a dose escalation part (Phase I) and a single-arm part (Phase II), in patients with recurrent SCLC who progressed after first-line platinum-based chemotherapy and who are candidates for second line therapy. No PK evaluation is planned in this study as nivolumab and ipilimumab are unlikely to alter plinabulin's PK, since the route of excretion is different.

This is an open-label Phase I/II study, with a dose escalation part (Phase I) and a single arm part (Phase II), in patients with recurrent SCLC.

In the Phase I part, patients will receive plinabulin at escalating doses in combination with nivolumab and ipilimumab. Doses of study drug will be administered as intravenous (IV) infusions in 21 day cycles. Patients will receive all study drugs on Day 1 of each cycle. After 4 treatment cycles, ipilimumab is stopped and patients continue treatment with nivolumab and plinabulin every 2 weeks (maintenance period) or until disease progression, development of unacceptable toxicity or one of the protocol-defined reasons for treatment discontinuation occurs.

At least 3 patients will be enrolled in each cohort, starting at 20 mg/m2 of plinabulin. The dose of plinabulin will be escalated in sequential patient cohorts after the safety data from the first cycle is reviewed. Thereafter the dose of plinabulin will be escalated to 30 mg/m2, provided that dose-limiting toxicities (DLTs) are not observed per the specified criteria, until the RP2D is determined.

In the Phase II part, up to 26 patients will be treated with the triple combination of plinabulin (at RP2D) + nivolumab + ipilimumab. Patients will continue treatment until disease progression, development of unacceptable toxicity or one of the protocol-defined reasons for treatment discontinuation occurs.

Inclusion Criteria:

The patients must satisfy all of the following inclusion/exclusion criteria in order to be eligible for the study:

• Must have signed and dated written informed consent form in accordance with regulatory and institutional guidelines.

• Males and females aged >18 years at time of consent.

• Histological or cytological confirmed extensive-stage SCLC

• Patients who progressed after at least 1 platinum-based chemotherapy regimen. Patients with platinum resistance (defined as recurrence or progression of disease within 90 days of completion of the platinum-based regimen) are eligible. For phase II, patients also must have been treated with at least one prior line of PD-1/PD-L1 therapy.

• Measurable disease according to RECIST v1.1 (Section 8) obtained by imaging within 28 days prior to study registration.

• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 within 14 days before registration and minimum life expectancy of at least 12 weeks.

• Treatment to be initiated at least 2 weeks since last dose of prior systemic anticancer therapy (chemotherapy, radiation, and/or surgery.

• Recovery to grade 1 of any clinically significant toxicity (excluding alopecia, grade 2 fatigue, vitiligo, endocrinopathies on stable replacement therapy) prior to initiation of study drugs.

• Female patients of childbearing potential have a negative pregnancy test at baseline. Females of childbearing potential are defined as sexually mature women without prior hysterectomy or who have had any evidence of menses in the past 12 months. However, women who have been amenorrheic for 12 or more months are still considered to be of childbearing potential if the amenorrhea is possibly due to prior chemotherapy, anti estrogens, or ovarian suppression.

  • Women of childbearing potential (i.e., menstruating women) must have a negative urine pregnancy test (positive urine tests are to be confirmed by serum test) documented within 14 days of study registration and within the 24-hour period prior to the first dose of study drug.
  • Sexually active women of childbearing potential enrolled in the study must agree to use 2 forms of accepted methods of contraception during the course of the study and for 23 weeks after their last dose of study drug. Effective birth control includes (a) intrauterine device plus 1 barrier method; (b) on stable doses of hormonal contraception for at least 3 months (e.g., oral, injectable, implant, transdermal) plus one barrier method; (c) 2 barrier methods. Effective barrier methods are male or female condoms, diaphragms, and spermicides (creams or gels that contain a chemical to kill sperm); or (d) a vasectomized partner.
  • For male patients who are sexually active and who are partners of premenopausal women: agreement to use 2 forms of contraception as in criterion 9b above during the treatment period and for 31 weeks after the last dose of study drug.

• Adequate laboratory values.

  • Absolute neutrophil count ≥1,000/µL
  • Platelet count ≥100,000/µL
  • Hemoglobin ≥9.0 g/dL
  • Total bilirubin ≤1.5 x upper limit of normal (ULN) or ≤3 x ULN for subjects with Gilbert's disease
  • Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤3.0 x ULN (≤5 x ULN if evidence of hepatic involvement by malignant disease)
  • Creatinine ≤ 1.5 x ULN or estimated glomerular filtration rate (eGFR) ≥40 mL/min/1.73m2
  • Lipase and Amylase ≤1.5 x ULN. Subjects with Lipase >1.5 x ULN may enroll if there are neither clinical nor radiographic signs of a pancreatitis.

Exclusion Criteria

Patients with any of the following will be excluded from participation in the study.

• Active interstitial lung disease (ILD) or pneumonitis or a history of ILD or pneumonitis requiring treatment with steroids. Prior history of radiation pneumonitis is allowed if pneumonitis was restricted to the field of radiation.
• History of ileus or other significant gastrointestinal disorder known to increase the risk of ileus or chronic bowel hypomotility
• 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 23 weeks (female) or 31 weeks (male) after the last dose of study drug.
• Must not have received CTLA-4 targeted therapy previously
• Treatment with any investigational agent within 28 days prior to registration for protocol therapy. Vaccination for SARS-CoV-2 is allowed as well as any therapy as required for the treatment of active COVID 19 infection.
• Known active symptomatic central nervous system (CNS) metastases and/or carcinomatous meningitis. Patients with neurological symptoms must undergo a head computed tomography (CT) scan or brain magnetic resonance imaging (MRI) to exclude brain metastasis. Patients whose brain metastases have been treated may participate provided there is no evidence of progression for at least 2 weeks after CNS-directed treatment, as ascertained by clinical examination or brain imaging.
• Known history of human immunodeficiency virus (HIV) or active hepatitis B (by surface antigen expression or polymerase chain reaction [PCR]) or active hepatitis C (by PCR) infection. NOTE: HIV testing is not required; Hepatitis B and C testing are required at screening.
• Diagnosis of immunodeficiency or is receiving systemic steroid therapy or any other form of immunosuppressive therapy within 7 days prior to study registration.
• Has active autoimmune disease that has required systemic treatment in the past 2 years (i.e., with use of disease modifying agents, corticosteroids, or immunosuppressive drugs) or a documented history of clinically severe autoimmune disease, or a syndrome that requires systemic steroids or immunosuppressive agents. Vitiligo, alopecia, hypothyroidism only requiring hormone replacement, psoriasis not requiring systemic treatment, celiac disease controlled by diet alone or conditions not expected to recur in the absence of an external trigger are permitted.
• A condition requiring systemic treatment with corticosteroids (>10 mg daily prednisone equivalent) or other immunosuppressive medications within 14 days prior to administration of study drugs.
• History of psychiatric illness or social situations that would limit compliance with study requirements. Has a history or current evidence of any condition, therapy, or laboratory abnormality that might confound the results of the trial, interfere with the patient's participation for the full duration of the trial, or is not in the best interest of the patient to participate, in the opinion of the treating investigator.
• Prior malignancies (except non-melanoma skin cancers, and the following in situ cancers: bladder, gastric, colon, endometrial, cervical/dysplasia, melanoma, or breast) unless a complete remission was achieved at least 2 years prior to study entry.
• Documented history of a cerebral vascular event (stroke or transient ischemic attack), unstable angina, myocardial infarction, or cardiac symptoms consistent with New York Heart Association (NYHA) Class III-IV within 6 months prior to their first dose of study drugs.
• Evidence of ongoing inadequately controlled hypertension (defined as baseline systolic blood pressure >160 mmHg or diastolic blood pressure >100 mmHg).
• Any active grade 3 or higher viral, bacterial, or fungal infection within 2 weeks of the first dose of the study drugs. Routine antimicrobial prophylaxis is permitted.