The study is being conducted to evaluate the safety, tolerability and efficacy of SHR-A2102/SHR-9839(sc) with Adebrelimab with or without other Antitumor Therapy in Subjects with Recurrent/Metastatic Head and Neck Squamous Cell Carcinoma.

To explore the reasonable dosage of SHR-A2102/SHR-9839（sc） for Subjects with Recurrent/Metastatic Head and Neck Squamous Cell Carcinoma

Inclusion Criteria:

1. Have the ability to give informed consent, have signed informed and able to comply with the treatment plan to visit the tests and other procedural requirements.
2. Subject with advanced or distant metastatic squamous cell carcinoma of the head and neck confirmed by histology or cytology.
3. At least one measurable lesion according to RECIST v1.1 criteria.
4. The ECOG score is 0 or 1.
5. Expected survival ≥12 weeks.
6. Male subjects whose partners are women of childbearing age and female subjects who are fertile are required to use highly effective contraceptive methods.

Exclusion Criteria:

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1. Subjects will not be screened if they meet any of the following conditions:

1. Primary tumor located in the nasopharynx, salivary glands, sinuses, skin, or squamous cell carcinoma of unknown primary origin;
2. Locally advanced patients who are candidates for curative surgery or local therapy and have the intention to undergo such treatment;

2. Known hypersensitivity to the investigational drug or any of its excipients, or a history of severe allergic reactions to other monoclonal antibodies.

3. Prior treatments or medications before the first dose of the study drug:

1. Use of any investigational drug within 4 weeks before the first dose;
2. Concurrent enrollment in another clinical trial, unless it is an observational (non-interventional) study or follow-up in an interventional study; 4. Active autoimmune disease or a history of autoimmune disorders. 5. Residual toxicity from prior anticancer therapy not resolved to ≤Grade 1 (CTCAE v5.0) (except for non-safety risks, such as alopecia) or not meeting the inclusion/exclusion criteria.

6. Uncontrolled or symptomatic active CNS metastases. 7. Symptomatic visceral metastases with imminent life-threatening complications .

8. Severe bone damage caused by tumor bone metastasis, including severe bone pain that is poorly controlled; pathological fractures in important areas that occurred within 6 months before the first medication or are expected to occur very soon; and spinal cord compression.

9. Known or suspected interstitial lung disease (ILD) or severe pulmonary conditions.

10. Other active malignancies within 3 years before study entry. 11. Have a history of immunodeficiency, including a positive HIV test result, or suffer from other acquired or congenital immune deficiency diseases, or have a history of organ transplantation and allogeneic bone marrow transplantation.

12. Clinically significant cardiovascular disease. 13. Active or chronic infections of clinical significance. 14. Pregnancy or lactation. 15. Other factors that, in the investigator's judgment, may lead to premature study discontinuation.