A Study of YL201 in Patients With Advanced Solid Tumors

Inclusion Criteria:

• Informed of the trial before the start of the trial and voluntarily sign their nameand date on the ICF

• Aged ≥18 years

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

• Adequate organ and bone marrow function

• Female patients of childbearing potential must agree to use a highly effective formof contraception and not donate, or retrieve for their own use, ova from the time ofscreening and throughout the study period, and for at least 5 months after the lastdose of atezolizumab or 6 months after the last dose of YL201, whichever is later.Male patients must agree to use a highly effective form of contraception and notfreeze or donate sperm from the time of screening and throughout the study period,and for at least 6 months after the last dose of YL201.

• Life expectancy of ≥3 months

• Able and willing to comply with protocol visits and procedures

• Have at least 1 evaluable tumor lesion according to Response Evaluation Criteria inSolid Tumors (RECIST) version 1.1.

• Pathologically confirmed diagnosis of an advanced solid tumor (SCLC, mCRPC, ESCC andNSCLC are preferred) for which standard treatment had proven to be ineffective orintolerable, or no standard treatment is available. For ES-SCLC patients in Arm C:no prior anti-cancer treatment

Exclusion Criteria:

• Concurrent enrollment in another clinical study, unless it is an observational (noninterventional) clinical study or during the follow-up period of aninterventional study

• Prior systemic anticancer treatment including chemotherapy, molecular -targetedtherapy, hormonal therapy, immunotherapy, or biological therapy within 3 weeksbefore the first dose of study drug (use of oral fluorouracil [eg, tegafur andcapecitabine] or small molecular-targeted therapy within 2 weeks or 5 half-lifeperiods [whichever is shorter]before the first dose; use of mitomycin ornitrosoureas within 6 weeks before the first dose; use of herbal medicine withantitumor indications or nonspecific immunomodulators [eg, thymosin, interferon, andinterleukin] within 2 weeks before the first dose).

• Prior radiation therapy, including palliative stereotactic radiation with abdominal,within 4 weeks before the first dose of study drug (if palliative stereotacticradiation therapy without abdominal, within 2 weeks)

• Undergone major surgery (not including diagnostic surgery) within 4 weeks before thefirst dose of study drug or expect major surgery during the study

• Undergone allogeneic hematopoietic stem cell transplantation (HSCT) before the firstdose of study drug, or autologous HSCT within 3 months before the first dose ofstudy drug

• Received systemic steroids (>10 mg/day of prednisone or its equivalent) or otherimmunosuppressive therapy within 2 weeks before the first dose of study drug.Received any live vaccine within 4 weeks before the first dose of study drug orintend to receive a live vaccine during the study

• Known human immunodeficiency virus (HIV) infection

• Active hepatitis B virus (HBV) or hepatitis C virus (HCV) infection. Active HBV isdefined as hepatitis B core antibody (HBcAb) or hepatitis B surface antigen (HBsAg)positive, and HBV DNA level above ULN at the study site; active HCV is defined aspositive hepatitis C antibody and HCV RNA level above ULN at the study site

• Unresolved toxicities from previous anticancer therapy, defined as toxicities (otherthan alopecia and pigmentation) not yet resolved to NCI CTCAE Grade ≤1, baseline, orthe level specified in the inclusion/exclusion criteria. Patients with chronic Grade 2 toxicities who are asymptomatic or adequately managed with stable medication maybe enrolled after discussion with the sponsor

• A history of severe hypersensitivity reactions to the drug substances, inactiveingredients in the drug product, or other mAbs

• Women who are breastfeeding or pregnant as confirmed by pregnancy tests performedwithin 7 days before the first dose