Non-randomized, open-label expansion study.

Investigating DF1001 as an immunotherapeutic agent targeting NK cells.

• Dose limiting toxicities
• Overall response rate
• Number of adverse events

General inclusion criteria

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 study entry and an estimated life expectancy of at least 3 months.
4. Baseline Left Ventricular Ejection Fraction (LVEF) ≥ 55% measured by echocardiography (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 as defined by World Health Organization (WHO) guidelines for 1 "highly effective" method or 2 "effective" methods.

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

1. Disease must be measurable with at least 1 unidimensional measurable lesion by RECIST 1.1.
2. Histologically confirmed NSCLC meeting stage criteria for stage IIIB, stage IV, or recurrent disease that has been confirmed to have HER2 expression (at least 1+, however, patients must not carry an erbb2 amplification) via archival or fresh biopsy tissue prior to study enrollment.
3. Patients must have recurrent or progressive disease during or after platinum doublet-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 by RECIST 1.1.
2. Histologically confirmed NSCLC meeting stage criteria for stage IIIB, stage IV, or recurrent disease that has been confirmed to have amplification of erbb2 via archival or fresh biopsy tissue prior to study enrollment.
3. Patients must have recurrent or progressive disease during or after platinum doublet-based chemotherapy.

1. Concurrent anticancer treatment (eg, cytoreductive therapy, radiotherapy [with the exception of palliative bone directed radiotherapy], immune therapy, or cytokine therapy except for erythropoietin), major surgery (excluding prior diagnostic biopsy), concurrent systemic therapy with steroids or other immunosuppressive agents, or use of any investigational drug within 28 days or 5 half-lives before the start of study treatment. Note: Patients receiving bisphosphonates are eligible provided 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 in this study within the last 3 years, with the exception of basal or squamous cell carcinoma 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-cell transplantation.
6. Significant acute or chronic infections (including historic positive test for human immunodeficiency virus [HIV], or active or latent hepatitis B or active hepatitis C tested during the screening window).
7. Preexisting autoimmune disease (except for patients with vitiligo) needing treatment with systemic immunosuppressive agents for more than 28 days within the last 3 years or clinically relevant immunodeficiencies (eg, dys-gammaglobulinemia or congenital immunodeficiencies), or fever within 7 days of Day 1.
8. Known severe hypersensitivity reactions to mAbs (≥ Grade 3 NCI-CTCAE v5.0), any history of anaphylaxis, or uncontrolled asthma (ie, 3 or more features of partly controlled asthma).
9. Persisting toxicity related to prior therapy > Grade 1 NCI-CTCAE v5.0, however alopecia 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 at rest
15. Significant ventricular arrhythmia (ventricular tachycardia) or higher-grade Atrioventricular block
    (AV-block; second-degree AV-block Type 2 [Mobitz 2] or third-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 > 100 mm Hg)
20. Clinically relevant uncontrolled cardiac risk factors, clinically relevant pulmonary disease or any
    clinically relevant medical condition in the opinion of the Investigator that may limit participation in
    this study.
21. Severe dyspnea at rest due to complications of advanced malignancy or requiring supplementary
    oxygen therapy.
22. All other significant diseases (e.g., inflammatory bowel disease), which, in the opinion of the
    Investigator, might impair the patient's ability to participate
23. Any psychiatric condition that would prohibit the understanding or rendering of informed consent.
24. Legal incapacity or limited legal capacity
25. Incapable of giving signed informed consent, which includes compliance with the requirements and
    restrictions listed in the informed consent form (ICF) and in this protocol.