A Study of ZL-1310 in Subjects With Small Cell Lung Cancer

Inclusion Criteria:

• Signed informed consent

• Participant with metastatic or extensive-stage small cell lung cancer (de novo, nottransformed) and for Part 1A and 1B must have documented disease progression duringor following a platinum-based chemotherapy regimen. For Part 1C and Part 4, no priorsystemic treatment for SCLC (including chemoradiotherapy for limited-stage SCLC).For Part 1B backfill, first-line setting: no prior systemic treatment for SCLC (including chemoradiotherapy for limited-stage SCLC); or, first-line maintenancesetting: participants have received at least 4 cycles of 1L induction therapy withcarboplatin or cisplatin, etoposide, and anti-PD-L1 inhibitor for ES-SCLC withongoing CR, PR, or SD per RECIST v1.1 assessed by the investigator. For Part 3,participants have received at least 4 cycles of 1L induction therapy withcarboplatin or cisplatin etoposide, and anti-PD-L1 inhibitor for ES-SCLC withongoing CR, PR, or SD per RECIST v1.1 assessed by the investigator.

• Adult men and women ≥18 years of age.

• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

• Subjects must have at least one measurable target lesion as defined by RECIST v1.1on CT, PET/CT, or MRI.

• Subjects must be willing to undergo a tumor biopsy or must provide archived tumortissue sample at screening per protocol guidelines.

• Life Expectancy >/= 3 months.

Exclusion Criteria:

• Participants with another known malignancy that is progressing or requires activetreatment within the last 2 years. Exceptions: basal cell carcinoma of the skin orlocalized squamous cell carcinoma of the skin with previously administered curativetreatment, in situ cervical cancer, or other cancers that do not require systemicanti-cancer therapies and will not impact life expectancy.

• Symptomatic or untreated brain metastasis requiring concurrent treatment. For Part 2, Part 3, and Part 4 the following subjects can be enrolled if they have a stableneurologic status for at least 2 weeks prior to the first dose of ZL-1310:

1. Subjects with untreated and asymptomatic brain metastases.

2. Subjects with treated brain metastases that are no longer symptomatic (i.e.without neurologic signs or symptoms), who require no treatment with steriodsor anticonvulsants and have recovered from the actue toxic effects ofradiotherapy.

• Subjects with leptomeningeal disease.

• Treatment with any systemic anti-cancer treatment or other investigational products/device within 3 weeks before first dose of study treatment.

• Non-palliative radiotherapy within 2 weeks prior to first dose of study treatment orhave had a history of radiation pneumonitis.

• Major surgery within 4 weeks of the first dose of study treatment.

• Hypersensitivity to any ingredient of the study treatment.

• Inadequate organ function (as defined in protocol) within 10 days prior to the firstdose of study treatment,

• Participants with a diagnosis of immunodeficiency or receiving chronic systemicsteroid therapy or any other form of immunosuppressive therapy within 14 days or 5half-lives before the first dose of study treatment, whichever is longer.

• Participants have received a live or live-attenuated vaccine within 30 days ofplanned start of study therapy.

• Impaired cardiac function or clinically significant cardiac disease within the last 3 months before administration of the first dose of the study treatment

• Lung-specific intercurrent clinically significant illnesses and any autoimmune,connective tissue, or inflammatory disorders, including but not limited topneumonitis.

• Pregnant or nursing (lactating) women.

• Participants who have been on concomitant strong CYP3A or CYP2D6 inhibitors within 14 days or 5 half-lives before the first study treatment, whichever is longer.

• For Part 1C and Part 4 (ZL-1310 in combination with Atezolizumab and Carboplatin),participants who received prior treatment with CD137 agonists or immune checkpointblockade therapies, anti-PD-1, and anti-PD-L1 therapeutic antibodies.

• For Part 1B (ZL-1310 in combination with Atezolizumab) and Part 1C (ZL-1310 incombination with Atezolizumab and Carboplatin), participants who received systemicimmunostimulatory agents (including but not limited to, IFNs and IL2) within 4 weeksor 5 drug-elimination half-lives, whichever is longer, prior to the initiation ofstudy treatment.