Study of DF1001 in Patients with Advanced Solid Tumors

Inclusion Criteria: General (applies to all cohorts)

1. Signed written informed consent.

2. Male or female patients aged ≥ 18 years.

3. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 at studyentry and an estimated life expectancy of at least 3 months.

4. Baseline Left Ventricular Ejection Fraction (LVEF) ≥ 55% measured byechocardiography (preferred) or multigated acquisition (MUGA) scan.

5. Adequate hematological function.

6. Adequate hepatic function.

7. Adequate renal function.

8. Effective contraception for women of child bearing potential (WOCBP) patients asdefined by World Health Organization (WHO) guidelines for 1 "highly effective"method or 2 "effective" methods.

Inclusion Criteria: NSCLC (HER2 Activated) Exploratory Efficacy Cohorts - Monotherapy and Combination with Sacituzumab Govitecan-hziy.

1. Have progression of unresectable locally advanced or metastatic NSCLC after lastsystemic therapy (as confirmed by investigator) or be intolerant of last systemictherapy.

2. Have HER2 overexpression status (IHC 2+ or 3+), or ERBB2 amplification, or HER2activating mutation

3. Have recurrent or progressive disease during or after platinum doublet-basedchemotherapy.

4. Have received and progressed on or after anti-PD-(L)1 therapy.

Inclusion Criteria: Metastatic Breast Cancer (HR+/HER2-) Exploratory Efficacy Cohort - Monotherapy and Combination with Sacituzumab Govitecan-hziy.

1. Documented evidence of HR+ metastatic breast cancer

2. Documented evidence of HER2- status.

3. Disease progression or recurrence after prior therapy.

Inclusion Criteria: Metastatic Breast Cancer (HER2+) Exploratory Efficacy Cohorts - Combination with Sacituzumab Govitecan-hziy

1. Have histologically confirmed HER2+ breast cancer.

2. Have received prior treatment with trastuzumab, pertuzumab, ado-trastuzumabemtansine (T-DM1), or trastuzumab deruxtecan (T-DXd).

3. Have progression of unresectable locally advanced metastatic breast cancer afterlast systemic therapy or be intolerant of last systemic therapy.

Inclusion Criteria: Dose Escalation

1. Evidence of objective disease, but participation does not require a measurablelesion.

2. Locally advanced or metastatic solid tumors, for which no standard therapy exists,or standard therapy has failed.

3. HER2 expression by immunohistochemistry and/or erbb2 amplification and/or erbb2activating mutations.

Inclusion Criteria: "3+3" Nivolumab Combination Cohort

1. Eligible to receive nivolumab per its label for a malignancy of epithelial origin;or

2. Have no standard therapy available, or standard therapy has failed, and must nothave received nivolumab prior to joining the study.

3. HER2 expression by immunohistochemistry and/or ebb2 amplification and/or erbb2activating mutations must be documented on either archival tissue or fresh tumorbiopsy.

Inclusion Criteria: "3+3" Nab paclitaxel Combination Cohort

1. Patients must be eligible for treatment with nab-paclitaxel per its label, or haveno standard therapy available, or standard therapy has failed.

2. HER2 expression by immunohistochemistry and/or erbb2 amplification and/or erbb2activating mutations must be documented on either archival tissue or fresh tumorbiopsy.

Inclusion Criteria: Safety/PK/PD Expansion Cohorts (Monotherapy and Combination Therapy).

1. Fresh tumor biopsy must be obtained during the screening window.

2. HER2 expression by immunohistochemistry (IHC).

3. Disease must be measurable with at least 1 unidimensional measurable lesion byRECIST 1.1.

Inclusion Criteria: Urothelial Bladder Cancer Expansion Cohort(s).

1. Disease must be measurable with at least 1 unidimensional measurable lesion byRECIST 1.1.

2. Histologically or cytologically documented locally advanced or metastatictransitional cell carcinoma of the urothelium (including renal pelvis, ureters,urinary urothelial, urethra).

3. Patients must have received a platinum containing chemotherapy and an anti PD-1 oranti PD-L1 for the treatment of urothelial bladder cancer.

Inclusion Criteria: Breast Cancer (HER2 Low) Expansion Cohort

1. Disease must be measurable with at least 1 unidimensional measurable lesion byRECIST 1.1

2. Histologically documented (metastatic or locally advanced) breast cancer.

3. Absence of erbb2 amplification by ISH and/or HER2 IHC of 0, 1+, or 2+.

4. Patient must have progressed after one line of systemic chemotherapy.

Inclusion Criteria: Breast Cancer (HER2 High) Expansion Cohort

1. Disease must be measurable with at least 1 unidimensional measurable lesion byRECIST 1.1

2. Histologically documented (metastatic or locally advanced) breast cancer.

3. Erbb2 amplification by ISH and/or HER2 IHC of 3+, or 2+. If Herceptest score is 2+,ISH results should demonstrate erbb2 amplification.

Inclusion Criteria: Basket erbb2 amplified Expansion Cohort

1. Disease must be measurable with at least 1 unidimensional measurable lesion byRECIST 1.1.

2. Documented history of erbb2 amplification.

3. Patients must have received at least one line of an approved or established therapy.

Inclusion Criteria: Gastric Cancer (HER2 High) Expansion Cohort

1. Disease must be measurable with at least 1 unidimensional measurable lesion byRECIST 1.1.

2. Advanced (unresectable/recurrent/metastatic) gastric cancer or cancer of thegastro-esophageal junction.

3. Tumor must have been declared HER2 positive.

Inclusion Criteria: Gastric Cancer (HER2 Low) Expansion Cohort

1. Disease must be measurable with at least 1 unidimensional measurable lesion byRECIST 1.1.

2. Advanced (unresectable/recurrent/metastatic) gastric cancer or cancer of thegastro-esophageal junction.

3. Tumor must have been declared HER2 low; ISH non-amplified and/or HER2 IHC of 0, 1+or 2+. If Herceptest score is 0, HER2 must be detected by IHC on at least 1+ of thetumor cells.

Inclusion Criteria: Esophageal Cancer (HER2 High) Expansion Cohort

1. Disease must be measurable with at least 1 unidimensional measurable lesion byRECIST 1.1.

2. Advanced (unresectable/recurrent/metastatic) esophageal cancer.

3. Tumor must have been declared HER2 positive.

Inclusion Criteria: Esophageal Cancer (HER2 Low) Expansion Cohort

1. Disease must be measurable with at least 1 unidimensional measurable lesion byRECIST 1.1.

2. Advanced (unresectable/recurrent/metastatic) esophageal cancer.

3. Tumor must have been declared HER2 low; ISH non-amplified and/or HER2 IHC of 0, 1+or 2+. If Herceptest score is 0, HER2 must be detected by IHC on at least 1+ of thetumor cells.

Inclusion Criteria: Non-small Cell Lung Cancer (HER2 Low) Expansion Cohort

1. Disease must be measurable with at least 1 unidimensional measurable lesion byRECIST 1.1.

2. Histologically confirmed NSCLC meeting stage criteria for stage IIIB, stage IV, orrecurrent disease that has been confirmed to have HER2 expression (at least 1+,however, patients must not carry an erbb2 amplification) via archival or freshbiopsy tissue prior to study enrollment.

3. Patients must have recurrent or progressive disease during or after platinumdoublet-based chemotherapy.

Inclusion Criteria: Non-small Cell Lung Cancer (HER2 High) Expansion Cohort

1. Disease must be measurable with at least 1 unidimensional measurable lesion byRECIST 1.1.

2. Histologically confirmed NSCLC meeting stage criteria for stage IIIB, stage IV, orrecurrent disease that has been confirmed to have amplification of erbb2 viaarchival or fresh biopsy tissue prior to study enrollment.

3. Patients must have recurrent or progressive disease during or after platinumdoublet-based chemotherapy.

Exclusion Criteria:

1. Concurrent anticancer treatment (eg, cytoreductive therapy, radiotherapy [with theexception of palliative bone directed radiotherapy], immune therapy, or cytokinetherapy except for erythropoietin), major surgery (excluding prior diagnosticbiopsy), concurrent systemic therapy with steroids or other immunosuppressiveagents, or use of any investigational drug within 28 days or 5 half-lives before thestart of study treatment. Note: Patients receiving bisphosphonates are eligibleprovided treatment was initiated at least 14 days before the first dose of DF1001.

2. Previous malignant disease other than the target malignancy to be investigated inthis study within the last 3 years, with the exception of basal or squamous cellcarcinoma of the skin or cervical carcinoma in situ.

3. Rapidly progressive disease.

4. Active or history of central nervous system (CNS) metastases.

5. Receipt of any organ transplantation including autologous or allogeneic stem-celltransplantation.

6. Significant acute or chronic infections (including historic positive test for humanimmunodeficiency virus [HIV], or active or latent hepatitis B or active hepatitis Ctested during the screening window).

7. Preexisting autoimmune disease (except for patients with vitiligo) needing treatmentwith systemic immunosuppressive agents for more than 28 days within the last 3 yearsor clinically relevant immunodeficiencies (eg, dys-gammaglobulinemia or congenitalimmunodeficiencies), or fever within 7 days of Day 1.

8. Known severe hypersensitivity reactions to mAbs (≥ Grade 3 NCI-CTCAE v5.0), anyhistory of anaphylaxis, or uncontrolled asthma (ie, 3 or more features of partlycontrolled asthma).

9. Persisting toxicity related to prior therapy > Grade 1 NCI-CTCAE v5.0, howeveralopecia and sensory neuropathy ≤ Grade 2 is acceptable.

10. Pregnancy or lactation in females during the study.

11. Known alcohol or drug abuse.

12. Serious cardiac illness

13. NYHA III of IV heart failure or systolic dysfunction (LVEF < 55%)

14. High-risk uncontrolled arrhythmias ie, tachycardia with a heart rate > 100/min atrest

15. Significant ventricular arrhythmia (ventricular tachycardia) or higher-gradeAtrioventricular block (AV-block; second-degree AV-block Type 2 [Mobitz 2] orthird-degree AV-block)

16. Angina pectoris requiring anti-anginal medication

17. Clinically significant valvular heart disease

18. Evidence of transmural infarction on ECG

19. Poorly controlled hypertension (defined by: systolic > 180 mm Hg or diastolic > 100mm Hg)

20. Clinically relevant uncontrolled cardiac risk factors, clinically relevant pulmonarydisease or any clinically relevant medical condition in the opinion of theInvestigator that may limit participation in this study.

21. Severe dyspnea at rest due to complications of advanced malignancy or requiringsupplementary oxygen therapy.

22. All other significant diseases (e.g., inflammatory bowel disease), which, in theopinion of the Investigator, might impair the patient's ability to participate

23. Any psychiatric condition that would prohibit the understanding or rendering ofinformed consent.

24. Legal incapacity or limited legal capacity.

25. Incapable of giving signed informed consent, which includes compliance with therequirements and restrictions listed in the informed consent form (ICF) and in thisprotocol .