This is an open-label, dose escalation and expansion study to evaluate the safety, tolerability, pharmacokinetics, and antitumor activity of autologous B4T2-001 CAR-T in subjects with advanced solid tumors including but not limited to advanced gastric or gastroesophageal junction (GEJ) adenocarcinoma, advanced pancreatic cancer, advanced non-small cell lung cancer (NSCLC), colorectal cancers (CRC) and metastatic breast cancer that tests positive for BT-001 target antigen according to Immunohistochemistry (IHC). The trial builds off first-in-human results from pilot study per clinicaltrials.gov ID: NCT05621486 to administer multiple infusions of B4T2-001 CAR-T without the need to give preparative chemotherapy (lymphodepletion).

This is an open-label dose escalation and expansion study to evaluate the safety, tolerability, pharmacokinetics (PK), and antitumor activity of lentiviral transduced autologous B4T2-001 CAR-T at up to four Dose Levels. Each treatment Block is composed of three Cycles of B4T2-001 CAR-T administered every 21 days by intravenous route without preparative chemotherapy (lymphodepletion). Subjects with advanced solid tumors will be enrolled. One or more Cycle(s) will be delayed as part of routine dosing plan until (i) absolute neutrophil count (ANC) greater than lower limit of normal (LLN) and (ii) resolution of grade >2 toxicity probably or definitely attributed to prior CAR-T and (iii) CAR-T available. Cycles will discontinue if (i) confirmatory imaging shows progressive disease (PD) and/or (ii) CAR-T cells are unavailable. Each additional Block(s) to begin at least 21 days after third Cycle of prior Block. The next patient(s) may be enrolled at least 21 days after completion of first Cycle of prior patient. The decision for dose escalation decision depends on the safety of first Cycle. Two subjects will be enrolled into each Dose Level. If none experiences a dose-limiting toxicity (DLT), the next cohort of two subjects will be enrolled into the next higher dose level. If a DLT is observed in one subject, four additional subjects will be added into the same dose level. If no additional DLT occur, DL will be escalated to the next higher dose level. If DLT occurs in two or more subjects among two to six subjects at a given dose level, dose escalation will be stopped, and the prior dose level will be expanded to six subjects to confirm maximum tolerated dose (MTD). If there is no more than one subject who experiences a DLT among those six subjects, that dose level is considered the MTD. Response to the treatment will be assessed before and after each Block. CT or MRI or PET for response assessment is anticipated every 60 days till day 180, then every 90 days till the end of the study. If complete response (CR), PD, or partial response (PR) on Day 60's assessment, another imaging study will be performed to confirm findings about 4 weeks later. The tumor marker(s) should be performed at the beginning and end of each Cycle All subjects will receive B4T2-001 CAR-T infusion at a healthcare facility, followed by frequently monitoring at a healthcare facility for at least 7 days to monitor for signs and symptoms of cytokine release syndrome (CRS) including immune effector cell-associated neurotoxicity syndrome (ICANS) and/or hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS). One dose of tocilizumab will be administrated on Day 7 of each Cycle as prophylaxis for CRS. The study follows sequential steps: patient screening, apheresis, bridging therapy (as needed), CAR-T infusions and follow up for up to two years. If the safety and tolerability are acceptable and recommended phase 2 dose (RP2D) is determined from the dose escalation stage, dose expansion will be considered.

Inclusion Criteria:

1. The subjects have been fully informed of the possible risks and benefits of participating in this study and have voluntarily signed the informed consent form (ICF).

2. Age: 18-70 years (including 18 and 70 years).

3. ECOG 0-1.

4. With an expected survival of more than 3 months.

5. Patients with histologically or cytologically confirmed locally advanced or metastatic "BT-001 positive" solid tumors. IHC should be within 6 months of apheresis, but maybe extended.

6. Preference for patients who have failed first- or second-line therapy.

7. Having measurable lesions according to RECIST 1.1 (or the latest version).

8. Maximum tumor size less than 4 cm according to RECIST 1.1 (or the latest version).

9. Having sufficient bone marrow, liver, kidney, and lung functions (based on the normal value of the clinical trial sites).

   • ANC and PLT ≥ LLN.
   • Without liver metastases, ALT, AST, or ALP ≤ 2.5×upper limit of normal (ULN); with liver metastases, ALT, AST, or ALP ≤ 5×ULN.
   • Serum creatinine (ScR) ≤ 1.5×ULN, or creatinine clearance > 50 mL/min (calculated according to Cockcroft Gault formula).
   • International normalized ratio (INR) ≤ 1.5×ULN, APTT ≤ 1.5×ULN.
   • Adequate oxygen saturation (≥ 95%) can be maintained without oxygen inhalation.

10. Male or female patients of childbearing potential agree to use effective methods of contraception (such as double-barrier contraceptive methods, condoms, oral or injectable contraceptives, and intrauterine devices) during the study period and within 1 year after infusion.

Exclusion Criteria:

1. Patients who have received the following anti-tumor treatments prior to apheresis:

   1. Cytotoxic therapy within 14 days or 28 days (for chemotherapy with high lymphocytic toxicity such as bendamustine, cyclophosphamide, ifosfamide, fludarabine, cladribine, etc.).
   2. Small molecule targeted therapy within 14 days or at least 5 half-lives, whichever is longer.
   3. Therapy with monoclonal antibody within 21 days including cetuximab.
   4. Therapy with immune checkpoint inhibitors and/or Avastin within 30 days of apheresis.
   5. Immunomodulatory therapy within 14 days.
   6. Radiotherapy within 14 days of apheresis.
   7. Traditional Chinese medicine with anti-tumor indications within 14 days of apheresis.
   8. Investigational agents or treatment within 28 days of apheresis.
   9. Previously treated with CAR-T/TCR-T cells and/or vaccine within 28 days of apheresis.

2. Previously treated with any BT-001-targeted therapy.

3. Brain metastases with central nervous system symptoms.

4. Pregnant (positive pregnancy test prior to dosing) or breast-feeding.

5. Allergic or suspected allergic reaction to any drug and related excipients specified in protocol, e.g., camelid antibody, pre-infusion medication (acetaminophen and diphenhydramine), serum albumin, tocilizumab (or biosimilars of tocilizumab that have been approved for CRS indication), Erbitux/ cetuximab, dimethyl sulfoxide (DMSO), and dextran 40.

6. Patients with positive hepatitis B surface antigen (HBsAg) or hepatitis B virus (HBV) deoxyribonucleic acid (DNA) > 100IU/mL or lower limit of the research center [Only when the detection limit of the research center is higher than 100IU/mL]), or patients with positive HCV antibody.

7. Patients with a history of immunodeficiency, including those who are HIV-positive, or patients with other acquired or congenital immune deficiency, or a history of organ transplantation.

8. Patients with concomitant or previous history of interstitial lung disease or interstitial pneumonia; presence of multiple metastatic lesions in the lungs or a single metastatic lesion ≥ 3 cm in length; patients with inflammation in the lungs or have received extensive radiotherapy.

9. Patients with uncontrolled active infection based on the investigator's judgment.

10. Patients who underwent major surgery within 2 weeks prior to apheresis and not fully recovered.

11. The toxicity of previous anti-cancer therapy, including immunotherapy has not returned to less than or equal to Grade 1 as specified in CTCAE v5.0 or the latest version (except for hair loss, Grade 2 peripheral neuropathy, and stable hypothyroidism treated with hormone replacement therapy).

12. Patients with a history of acute myocardial infarction, unstable angina pectoris, stroke, or transient ischemic attack within 6 months prior to the enrollment, or with NYHA Class 2 or higher congestive heart failure.

13. Patients with chronic diseases requiring treatment with systemic corticosteroids or other immunosuppressants, received systemic corticosteroids (≥ 70 mg prednisone or equivalent dose of other corticosteroids) or other immunosuppressants within 7 days before apheresis, except for the following cases: local, ocular, intra-articular, intranasal, and inhaled glucocorticoid treatment; short term use of glucocorticoids for preventive treatment (such as prevention of contrast medium allergy).

14. Patients with autoimmune diseases.

15. Patients with Crohn's Disease.

16. Patients with a history of uncontrollable mental illness.

17. Any condition in which the investigator considers that the subject is not suitable to participate in the study.