Pan-T Booster Co-expressing MSLN CAR T Cell Therapy in Advanced/Metastatic Solid Tumors

Phase I/II Study of Pan-T Booster Co-expressing MSLN CAR T Cell Therapy in Advanced/Metastatic Solid Tumors

In preclinical study, investigators have demonstrated that the newly developed pan-T booster (harbouring CD40 agonist and one T cell costimulator agonist) co-expressing MSLN CAR T cell possess more powerful antitumor activity than previously reported MSLN-CAR T cells. In this clinical trial, enrolled patients receive an initial dose of pan-T booster co-expressing MSLN CAR T cells at 1×10^6 cells/kg based on the basic principle of dose escalation design, in order to evaluate the safety, feasibility, pharmacokinetics/pharmacodynamics, and efficacy of pan-T booster co-expressing MSLN CAR T cell in vivo.

In this study, investigators have developed a novel CAR T cell system targeting mesothelin (MSLN) antigen, termed as Pan-T booster (harbouring CD40 agonist and one T cell costimulator agonist) co-expressing MSLN CAR T cell. Preclinical study demonstrated that this novel pan-T booster co-expressing MSLN CAR T cell possess more powerful antitumor activity than previously reported MSLN-CAR T cells. In this clinical trial, enrolled patients receive an initial dose of pan-T booster co-expressing MSLN CAR T cells at 1×10^6 cells/kg based on the basic principle of dose escalation design, in order to evaluate the safety, feasibility, pharmacokinetics/pharmacodynamics, and efficacy of pan-T booster co-expressing MSLN CAR T cell in vivo. The level of CAR-T cell expansion and the duration of expansion are important determining factors for subsequent dose escalation infusions (3×10^6 cells/kg and 6×10^6 cells/kg). Repeated infusion, immune checkpoint inhibitor (such as anti-PD1/PD-L1) or local therapy (radiotherapy) are allowed when patients achieve clinical benefit and the level of CAR-T cell expansion declines to low level.

In the 3 patients receiving the first dose treatment, we observed high levels of expansion of both total T cells and CAR T cells in the PB after CAR T cell infusion (CAR T > 300 per microliter, total T cells reaching 10 times the number of CAR T cells), one patient experienced a grade 2 pulmonary toxicity and transient liver dysfunction during the CAR T cell expansion period (infusion 14 days later), transient marked enlargement of the spleen, and required to be treated with glucocorticoids and ruxolitinib to control T cell toxicity. Efficacy monitoring showed that some target lesion clearance or reduction could be achieved within 2-4 weeks after CAR T infusion. Based on these observations, it was concluded that low-dose CAR T infusion (CAR+T cells 1×10^6 cells/kg) could achieve the sufficient level of CAR T cell expansion, and the initially planned CAR T dose escalation was dispensable. Subsequent patients after May 10th, 2024, will all be treated using 1×10^6 cells/kg dose.

Inclusion Criteria:

• 1. Age from 18 to 75 years with estimated life expectancy >3 months.
• 2. Histopathological confirmed advanced or metastatic solid tumors failed to at least first-line treatment or initially diagnosed advanced/metastatic solid tumors that have no NCCN guideline recommended standard first-line therapy. Mesothelin antigen expression percentage >＝10%.
• 3. Have at least one measurable target lesion.
• 4. Fresh solid tumor samples or formalin-fixed paraffin embedded tumor archival samples within 6 months are necessary; Fresh tumor samples are preferred. Subjects are willing to accept tumor rebiopsy in the process of this study.
• 5. Previous treatment must be completed for more than 4 weeks prior to the enrollment of this study, and subjects have recovered to <= grade 1 toxicity.
• 6. Have an Eastern Cooperative Oncology Group performance status (ECOG) of 0 or 2 at the time of enrollment.
• 7. Have adequate organ function, which should be confirmed within 2 weeks prior to the first dose of study drugs.
• 8. Previous treatment with anti-PD-1/PD-L1 antibodies are allowed.
• 9. Ability to understand and sign a written informed consent document.
• 10. Women of child-bearing potential must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry, and up to 90 days after the last dose of the drug.

Exclusion Criteria:

• 1. Active, known or suspected autoimmune diseases.
• 2. Known brain metastases or active central nervous system (CNS). Subjects with CNS metastases who were treated with radiotherapy for at least 3 months prior to enrollment, have no central nervous symptoms and are off corticosteroids, are eligible for enrollment, but require a brain MRI screening.
• 3. Subjects are being treated with either corticosteroids (>10 mg daily prednisone equivalent) or other immunosuppressive medications within 14 days of enrollment.
• 4. History of severe hypersensitive reactions to other monoclonal antibodies.
• 5. History of allergy or intolerance to study drug components.
• 6. Substance abuse, medical, psychological or social conditions that may interfere with the patient's participation in the study or evaluation of the study results.
• 7. History or concurrent condition of interstitial lung disease of any grade or severely impaired pulmonary function.
• 8. Uncontrolled intercurrent illness, including ongoing or active systemic infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia (excluding insignificant sinus bradycardia and sinus tachycardia) or psychiatric illness/social situations and any other illness that would limit compliance with study requirements and jeopardize the safety of the patient.
• 9. History of human immunodeficiency virus (HIV) infection or acquired immunodeficiency syndrome (AIDS).
• 10. Pregnant or breast-feeding. Women of childbearing potential must have a pregnancy test performed within 7 days before the enrollment, and a negative result must be documented.
• 11. Previous or concurrent cancer within 3 years prior to treatment start EXCEPT for curatively treated cervical cancer in situ, non-melanoma skin cancer, superficial bladder tumors [Ta (non-invasive tumor), Tis (carcinoma in situ) and T1 (tumor invades lamina propria)].
• 12. Vaccination within 30 days of study enrollment.
• 13. Active bleeding or known hemorrhagic tendency.
• 14. Subjects with unhealed surgical wounds for more than 30 days.
• 15. Being participating any other trials or withdraw within 4 weeks.