A Phase I/II, Open-Label, Multi-Center Study of ALE.C04 as a Single Agent and in Combination With Pembrolizumab in Adult Patients With Recurrent or Metastatic Head and Neck Squamous Cell Carcinoma

The study comprises a phase I and a phase II. The phase I dose escalation part for both ALE.C04 monotherapy and in combination with pembrolizumab and a recommended dose for expansion (RDE) part for both ALE.C04 monotherapy and in combination with pembrolizumab. The phase II comprises a 1:1 randomized 2 arms assessing 2 dose levels of ALE.C04 as monotherapy and a 1:1 randomized 2 arms assessing ALE.C04 and pembrolizumab given in combination versus pembrolizumab monotherapy

Inclusion Criteria:

1. Be willing and able to provide written informed consents
2. Be 18 years of age on day of signing informed consent.
3. Have histologically or cytologically confirmed Recurrent or Metastatic (R/M) Head and Neck Squamous Cell Carcinoma (HNSCC) that is considered incurable by local therapies.
4. Have provided tissue for claudin-1 (CLDN1), programmed death ligand-1 (PD-L1) and biomarker analysis in a central Clinical Laboratory Improvement Amendments (CLIA)-certified laboratory.
5. Have measurable disease based on RECIST 1.1 as determined by the site.
6. Have a performance status of 0 or 1 on the Eastern Cooperative Oncology Group (ECOG) Performance Scale.
7. Have results from testing of human papillomavirus (HPV) status for oropharyngeal cancer

Exclusion Criteria:

1. Has progressive disease (PD) within 6 months of completion of curatively intended systemic treatment for locoregionally advanced HNSCC (Phase II randomized combination part only).
2. Has had radiation therapy (or other non-systemic therapy) within 2 weeks prior to randomization or patient has not fully recovered (i.e., ≤Grade 1 or at baseline) from adverse events due to a previously administered treatment. Palliative radiotherapy to a limited field is allowed.
3. Severe immune-related adverse events leading to discontinuation of prior immune-oncology agent only for Phase I dose escalation monotherapy and combination and Phase II monotherapy.
4. Has known active central nervous system (CNS) metastases and/or carcinomatous meningitis.
5. Dermatological conditions requiring active pharmacological treatment including psoriasis, atopic dermatitis, excessively dry skin or recurrent conjunctivitis, scleroderma, vitiligo, or any other active autoimmune dermatological disorder.
6. Has a history or current evidence of any condition, therapy, or laboratory abnormality that might confound the results of the clinical study, interfere with the patient's participation for the full duration of the clinical study, or is not in the best interest of the patient to participate, in the opinion of the treating investigator.
7. Has received prior therapy with an anti-programmed death (PD)-1, anti-PD-L1 or anti-PD-L2 (Phase II randomized combination part only).