The goal of this Phase 2 clinical trial is to learn if the combination of Camrelizumab and Palbociclib is a safe and effective treatment when given before surgery (neoadjuvant therapy) for patients with esophageal squamous cell carcinoma (ESCC) that can be surgically removed. Camrelizumab is an immunotherapy drug that helps the immune system fight cancer, and Palbociclib is a targeted therapy drug that stops cancer cells from growing.

The main questions it aims to answer are:

Is the combination of Camrelizumab and Palbociclib safe for patients to receive before their surgery? How effective is this treatment combination in shrinking tumors prior to surgery?

Inclusion Criteria:

• Patients diagnosed with esophageal squamous cell cancer by gastroscopic biopsies.
• The primary tumor should be located in the thorax and evaluated resectable( cT1b-T3N1-3M0, cT3N0M0) by CT/MRI/EUS
• The patients should be at the range of 18-75 years old, Eastern Cooperative Oncology Group (ECOG) 0-1.
• The patients should have no functional disorders in major organs. Blood routine tests, as well as lung, liver, kidney, and heart functions should be basically normal.
• The patients should be able to understand our research and be willing to accept surgical treatment and sign the informed consent.

Exclusion Criteria:

• The stage of tumor is T4b (AJCC/International Union Against Cancer (UICC) 8th Edition) and cannot be resected.
• Currently undergoing other chemotherapy, radiotherapy, targeted therapy or immunotherapy.
• History of other malignancies.
• Have an active autoimmune disease requiring systemic treatment or a documented history of clinically severe autoimmune disease.
• Any history of allergic disease, or a sever hypersensitivity reaction to drugs, or allergy to the study drug components.
• Presence of serious medical diseases, such as grade II and above cardiac dysfunction (NYHA criteria), ischemic heart diseases, etc.
• The patients with severe systematic intercurrent diseases, including active infection or poorly controlled diabetes, coagulation disorders, hemorrhagic tendency, or those undergoing thrombolysis or anticoagulant therapy etc. are excluded from the study.
• Female participants who test positive for a serum pregnancy test, are in the lactation period, or are at a childbearing stage and unwilling to use contraception measures during the research are excluded.
• Received any investigational drug within 4 weeks prior to the first dose, or concurrently enrolled in another clinical trial.
• Any other factors that are not suitable for inclusion in this study judged by investigators.