1) Voluntarily sign the Informed Consent Form (ICF) with date after being comprehensively informed of study information before initiation.

2) Aged ≥ 18 years.

3) Willing and able to comply with all study procedures.

4) Tumor types Phase I - Dose Escalation and Backfill

Monotherapy

• Patients with histologically or cytologically confirmed advanced solid tumors.

• Patients with documented disease progression following standard treatments, with no standard treatment options available, or for whom standard treatments are not applicable currently, or who are unlikely to derive clinical benefit from therapies approved by the local regulatory authority.

Combination therapy

• Patients with histologically or cytologically confirmed EOC (including primary peritoneal cancer and fallopian tube cancer).

• For YL205 in combination with bevacizumab: Patients with documented disease progression following standard treatments, with no standard treatment options available, or for whom standard treatments are not applicable currently, or who are unlikely to derive clinical benefit from therapies approved by the local regulatory authority.

• For YL205 in combination with carboplatin: patients must have history of disease progression for more than 6 months after completing the last platinum-based therapy.

• Patients must have disease progression, as evidenced by radiographic, biochemical, or clinical criteria (e.g., new ascites, pleural effusion, or worsening symptoms).

Phase II - Dose Expansion

• Cohort A

➢ Histologically or cytologically confirmed as high-grade serous ovarian cancer, including fallopian tube epithelial cancer and primary peritoneal cancer.

➢ Meet the criteria for platinum-resistance:

• Patients who have only received first-line platinum-based chemotherapy (≥ 4 cycles), achieved a Partial Response (PR) or Complete Response (CR) during treatment, and experienced disease progression within 3 to 6 months after the end of treatment.

• Patients who have received ≥ 2 prior lines of systemic therapy must have experienced disease progression within 6 months after receiving at least 4 cycles of platinum-based therapy.

➢ Radiographic disease progression after prior receipt of at least one line of systemic anti-tumor therapy.

• Cohort B

➢ Histologically or cytologically confirmed advanced renal cell carcinoma.

➢ Radiographic disease progression after prior receipt of at least one line of systemic anti-tumor therapy.

• Cohort C

➢ Histologically or cytologically confirmed locally advanced or metastatic NSCLC with or without actionable genomic alterations (AGA) (refer to Appendix 10 for details), and not eligible for curative surgery or radiotherapy.

➢ For adenocarcinoma or NSCLC containing adenocarcinoma components, genetic testing must be performed. For patients with other pathological types such as squamous cell carcinoma, genetic testing is not required.

➢ For patients with AGA, disease progression on AGA-specific targeted therapy approved by the local regulatory authority is required, or intolerance to such therapy, or if targeted therapy is not applicable.

➢ For patients without AGA, previously received at least one line of systemic therapy for advanced NSCLC, including platinum-containing chemotherapy.

➢ Radiographic disease progression after prior receipt of at least one line of systemic anti-tumor therapy.

• Cohort D

➢ Histologically or cytologically confirmed advanced endometrial carcinoma, including endometrioid, serous, clear cell, carcinosarcoma, undifferentiated, dedifferentiated, mixed, and other rare endometrial carcinoma.

➢ Radiographic disease progression after prior receipt of at least one line of systemic anti-tumor therapy .

➢ Patients who received platinum-based adjuvant therapy are eligible if recurrence occurred < 6 months after completion; otherwise, they must have received another line of platinum-based therapy in the metastatic setting.

➢ Patients with unknown HER2 expression is eligible. Patients who are HER2- positive must have received prior HER2-targeted therapy.

5) ECOG PS score of 0 or 1 (refer to Appendix 1 for details).

6) Organ function must meet the following criteria:

• Hemoglobin ≥ 9.0 g/dL (have not received transfusion, albumin, or erythropoietin treatment within 14 days before the first dose).

• Absolute neutrophil count (ANC) ≥ 1.5×109 /L (have not received granulocyte colonystimulating factor or granulocyte-macrophage colony-stimulating factor treatment within 14 days before the first dose).

• Platelet count (PLT) ≥ 100×109 /L (have not received platelet transfusion, thrombopoietin, interleukin-11, or eltrombopag treatment within 14 days before the first dose).

• Adequate hepatic function: ‒ Total bilirubin ≤ 1.5×ULN with the exception that potential patients with known Gilbert disease: total bilirubin ≤ 3×ULN.

• Creatinine clearance ≥ 60 mL/min (calculated using the Cockcroft-Gault formula, refer to Appendix 5) or serum creatinine ≤ 1.5×ULN.

• Activated partial thromboplastin time (APTT) and international normalized ratio (INR) ≤1.5 × ULN, except for patients receiving anticoagulant therapy, who must have a stable anticoagulant therapy regimen and have activated partial thromboplastin time (APTT) and international normalized ratio (INR) within the therapeutic range deemed appropriate by the investigator.

• Serum albumin ≥ 25 g/L (2.5 g/dL).

7) Patients in the dose escalation must have at least one radiographically evaluable lesion. Patients in backfill and dose expansion must have at least one measurable extracranial lesion (non-irradiated area). Patients with radiographically evaluable but not measurable extracranial lesion in the backfill part may be enrolled after case-by-case discussion with the sponsor. Assessments will be conducted according to the Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 (refer to Appendix 3 for details).

8) Life expectancy ≥ 3 months.

9) Female patients of childbearing potential must agree to use effective contraception from the screening period throughout the entire study period and for at least 6 months after the last administration of the study drug, and must not donate or retrieve ova for their own use. Male patients must agree to use effective contraception from the screening period throughout the entire study period and for at least 6 months after the last administration of the study drug, and must not freeze or donate sperm (refer to Appendix 7).

10) Patients must provide 5 slides of archived or fresh tumor tissue samples, and 10-15 paraffin scrolls of archived or fresh tumor tissue samples, or tumor tissue block. Patients in dose escalation of monotherapy who cannot provide tumor samples, or whose samples are inadequate or expired, may also be enrolled after discussion with the sponsor. Tumor tissue slide samples must be provided from patients in the backfill and dose expansion for monotherapy and dose escalation for combination therapy. Patients with inadequate samples may be enrolled after case-by-case discussion with the sponsor

11) Able and willing to comply with the study protocol's planned visits and procedures.

1) Expansion Cohort A:

• Mixed types of high-grade serous type.

• Primary platinum drug refractory: defined as progression within 3 months after the last dose of first line platinum-based therapy or lack of therapeutic effect.

Expansion Cohort D:

• Mesenchymal tumors such as Eendometrial stromal sarcoma or mixed epithelial and mesenchymal tumors or any mixed types of sarcoma.

2) Prior treatment with an agent targeting NaPi2b (including antibodies, ADC, chimeric antigen receptor T cell [CAR-T], and other drugs).

3) Prior treatment with topoisomerase I inhibitors or ADCs that consist of topoisomerase I inhibitors, including but not limited to topotecan, irinotecan, and trastuzumab deruxtecan.

4) Simultaneous participation in another clinical study, except for observational (noninterventional) clinical studies or during the follow-up period of an interventional study.

5) Inadequate washout period for prior anti-tumor therapies before the first dose, defined as follows:

• Any cytotoxic chemotherapy or small molecule targeted therapy (excluding EGFRTKIs) administered less than 4 weeks or 5 half-lives before first dosing, whichever is shorter; for patients with NSCLC confirmed by histology or cytology who are receiving EGFR-TKI therapy at the time of signing the ICF, continuation of EGFRTKI therapy is allowed until 5 days before C1D1.

• Endocrine therapy < 3 weeks.

• Monoclonal antibodies or other biological therapies < 3 weeks.

• Traditional Chinese medicines with anti-tumor indications (refer to Appendix 6) < 2 weeks.

• Whole brain radiation therapy < 4 weeks or stereotactic brain radiation therapy < 4 week.

• Radiation therapy to more than 30% of bone marrow or wide-field radiation therapy < 4 weeks or palliative radiation < 2 weeks.

6) Received radiotherapy within 4 weeks prior to the first dose, including abdominal palliative stereotactic radiotherapy (if non-abdominal palliative three-dimensional conformal radiotherapy, then within 2 weeks).

7) Received major surgery within 4 weeks prior to the first dose (excluding diagnostic surgery) or plans to undergo major surgery during the study. Underwent interventional or ablative surgery aimed at treating tumor within 2 weeks prior to the first dose of the study drug.

8) Previously received allogeneic bone marrow transplant or solid organ transplant.

9) Received any live vaccine within 4 weeks before the first dose or plan to receive a live vaccine during the study.

10) A history of leptomeningeal carcinomatosis or carcinomatous meningitis.

11) Brain metastasis or spinal cord compression, except in the following cases:

• Patients with asymptomatic brain metastasis may be enrolled if their brain metastatic lesions are not new lesions, the lesions have not increased in size, and they do not require immediate local or systemic therapy (e.g., mannitol or corticosteroids).

• Patients may be enrolled if their brain metastatic lesions have been treated and are stable (brain imaging at least 4 weeks before the first dose shows stable lesions, no new neurological symptoms, and no need for immediate local or systemic therapy within 2 weeks before the first dose), and there is no evidence of new or enlargement of original brain metastatic lesions.

12) Uncontrolled or clinically significant cardiovascular and cerebrovascular diseases, including but not limited to:

• History of symptomatic cardiac failure congestive (New York Heart Association [NYHA] functional classification of II to IV, refer to Appendix 2) or any arterial thromboembolism (e.g., myocardial infarction, angina unstable, cerebrovascular accident, transient ischemic attack) within 6 months before the first dose.

• Underwent percutaneous coronary arterial angioplasty or coronary artery bypass within 6 months before the first dose.

• Previous occurrence of pulmonary embolism or serious arteriovenous thrombosis events such as deep vein thrombosis occurring within 3 months before the first dose.

• Uncontrolled hypertension; hypertension not controlled after combined treatment with two or more medications, with systolic blood pressure ≥ 150 mmHg and/or diastolic blood pressure ≥ 90 mmHg after antihypertensive treatment.

• Other arrhythmias or clinical conditions that the investigator believes may increase the risk of QT interval prolongation, such as complete left bundle branch block, thirddegree atrioventricular block, congenital long QT syndrome, severe hypokalemia, a family history of long QT syndrome or a family history of sudden death under 40 years of age.

• At rest, the corrected QT interval by Fridericia Formula (QTcF) calculated from a 12-lead electrocardiogram according to Fridericia's formula (refer to Appendix 4) is prolonged to > 470 ms (Note: if the initial investigation is abnormal, repeat twice within 48 hours and average the three measurements to determine eligibility).

• Left ventricular ejection fraction (LVEF) by echocardiogram (ECHO) < 50%.

13) Concomitant lung disorders of significant clinical importance, including but not limited to:

• Dyspnea at rest due to advanced tumor malignant, or other diseases requiring continuous oxygen therapy.

• Prior or current interstitial lung disease (ILD)/interstitial pneumonia, drug-induced ILD, radiation pneumonitis requiring steroid treatment, or clinical manifestations or high-risk factors suspected to be interstitial lung disease.

• Moderate to severe lung disorders that severely affect respiratory function, such as severe chronic obstructive pulmonary disease; any autoimmune, connective tissue, or inflammation diseases (e.g., rheumatoid arthritis, Sjögren's syndrome, sarcoidosis) recorded at screening that cause or are suspected to cause pulmonary involvement.

• Prior unilateral pneumonectomy.

14) With significant symptoms or unstable third-space fluid accumulation (such as pleural effusion, ascites, pericardial effusion) requiring repeated drainage, deemed too frequent or clinically significant in the judgment of the sponsor and investigator.

15) History of gastrointestinal perforation and/or fistula within 6 months prior to the first dose, patients have active gastric ulcer, duodenal ulcer, colitis ulcerative, or other gastrointestinal diseases that the investigator considers may cause hemorrhage, perforation, or obstruction.

16) Severe or poorly controlled diabetes mellitus, including: ① Diabetic ketosis or hyperosmolar state within 6 months prior to the first dose; ② Patients with glycosylated hemoglobin test value ≥ 8.0% during the screening period (Note: Newly diagnosed diabetes mellitus is not considered well-controlled diabetes mellitus unless after at least 8 weeks of hypoglycemic therapy and all recorded blood glucose test values during the screening period are < 13.9 mmol/L, including home blood glucose monitoring records; then they can be enrolled).

17) Had severe infection before the first dose (Patients who have severe uncontrolled infections (e.g., ≥ NCI CTCAE v5.0 Grade 3), such as severe pneumonia requiring hospitalization, bacteremia, infectious complications, etc., or active infections requiring systemic therapy within two weeks prior to the first dose. Patients receiving prophylactic anti-infective therapy (e.g., to prevent a urinary tract infection or chronic obstructive pulmonary disease exacerbation) may be eligible after discussion with the sponsor.

18) Patients with human immunodeficiency virus (HIV) infection. Inclusion is allowed if none of the following are met:

• History of an acquired immunodeficiency syndrome-defining opportunistic infection in the last 1 year.

• Irregular anti-retroviral therapy compliance.

• Anti-retroviral therapy started < 3 months before the start of trial treatment. • CD4+ count of < 300/µL.

• Viral load of > 400 copies/mL. Note: Patients with HIV should be under the care of an infectious disease specialist (or equivalent per local regulations); HIV-related tests at screening and follow-up during the duration of trial treatment should be sent to the sponsor.

19) Patients who test positive for syphilis antibodies with positive titer tests.

20) Active hepatitis B virus (HBV) or hepatitis C virus (HCV) infection. Definition of Active HBV Patients who are positive for hepatitis B surface antigen (HBsAg) and/or hepatitis B core antibody (HBcAb), with HBV deoxyribonucleic acid (DNA) levels higher than the lower limit of quantification at the site; active HCV is defined as patients who are hepatitis C antibody positive with HCV RNA levels higher than the lower limit of quantification at the site.

21) Unresolved toxicities from prior anti-tumor therapies, defined as toxicities (excluding alopecia and pigmentation) not yet resolved to ≤ NCI CTCAE v5.0 Grade 1, baseline level, or the level specified in the inclusion/exclusion criteria. Patients with chronic Grade 2 toxicity might be eligible after discussion with sponsor if asymptomatic or well controlled by medication.

22) History of severe allergic reactions to the drug, inactive ingredients in the drug product, or other monoclonal antibodies (e.g., anaphylactic shock or prior severe infusion reactions).

23) Women who have a pregnancy test confirming pregnancy or are currently breastfeeding.

24) Any disease, medical condition, system organ dysfunction, or social situation, including but not limited to mental illness or drug/alcohol abuse, that the investigator believes may interfere with the patient's ability to sign the informed consent form, affect patient compliance, or impact the interpretation of study results.

25) Any other primary tumor malignant within 5 years prior to the first dosing of the study drug, except for adequately excised non-melanoma skin cancer, cured carcinoma in situ, or other cured solid tumors.

26) History of bowel obstruction (including sub-occlusive disease) related to underlying disease within 6 months before the start of study treatment.

27) History of abdominal fistula, gastrointestinal perforation, intra-abdominal abscess, or evidence of rectosigmoid involvement by pelvic examination, bowel involvement on computed tomography scan, or clinical symptoms of bowel obstruction.

28) Prior radiotherapy to the pelvis or abdomen (Dose Escalation phase only).

Additional Exclusion Criteria for YL205 + bevacizumab Combination Therapy

29) History of bleeding tendency or coagulopathy and/or clinically significant bleeding symptoms or risks within 4 weeks prior to the first dose enrollment, including but not limited to:

• Hemoptysis (defined as ≥ 0.5 teaspoons of fresh blood or small blood clots), transient hemoptysis associated with diagnostic bronchoscopy is allowed.

• Epistaxis (bloody nasal discharge is allowed).

• Patients currently on full-dose anticoagulants or antiplatelet medications for prophylactic or therapeutic purposes who have not achieved a stable condition prior to the first dose enrollment are not eligible for inclusion.

30) Imaging examinations at screening revealing that patients have the following conditions: Imaging confirmed tumor invasion of major vessels (such as central pulmonary artery, central pulmonary vein, aorta, brachiocephalic artery, common carotid artery, subclavian artery, superior vena cava, etc.) or tumor invasion of vital organs (such as heart, trachea, esophagus, main bronchus [excluding segmental bronchus]) or the investigator considers that patients have the risk of developing esophagotracheal fistula or esophagopleural fistula.

31) Imaging evidence of tumor encasing large vessels with vascular stenosis, or the presence of cavitary lesions or necrosis within pulmonary lesions that, in the judgment of the investigator, would pose a risk of hemorrhage during the study period.

32) Non-healing wounds, ulcers, or bone fractures.

33) History of posterior reversible encephalopathy syndrome.

34) Clinically significant proteinuria: urine-protein (UPC) ratio ≥ 1.0 or urine dipstick result ≥ 2+; patients with UPC ratio ≥ 1.0 or ≥ 2+ proteinuria should undergo 24-hour urine collection and must show result ≤ 1 gram of protein in 24-hour period.