Abstract 966: Injection of oxaliplatin into liver metastases will be required to break immune suppression in colorectal carcinoma patients
Authors: Jessup John Milburn , Taub Daniel D. 
Published: September 2020

Introduction: The purposes of this study were to define the optimal concentration of Oxaliplatin (L-OHP) that induces Immunogenic Cell Death (ICD) in Colorectal Carcinomas (CRC) and whether this can be achieved by such standard first line chemotherapy as mFOLFOX-6. We have previously shown that intratumoral 80 microM L-OHP combined with oncolytic virus causes complete regression of 6 mm diameter CT26 tumors in 40% of BALB/c mice whereas L-OHP or virus alone inhibits tumor growth by 60%. As virus proceeds through regulatory approval, we plan to translate this treatment to the clinic initially with image guided injection of L-OHP into CRC liver metastases in a Phase 0 neoadjuvant trial.

Methods: 20 - 250 microM L-OHP was tested in vitro on human CRC lines Clone A, CX-1 and LS174T for externalization of Calreticulin, the critical first step in ICD. ATP and HMBG1 were also measured by luminescence and ELISA. Externalization was measured over 4-96 hr by fluorescence microscopy and flow cytometry. In addition, a literature search was performed for L-OHP concentrations in liver metastasis and active L-OHP concentrations by AUC0-4 after systemic and intrahepatic administration.

Results: 80 microM was the optimal concentration with maximal externalization over 4 - 24 hours with 20 - 60% of cells positive for Calreticulin. Concentrations of 20 - 40 microM provided lesser Calreticulin externalization while concentrations greater than 160 microM L-OHP blocked Calreticulin externalization. ATP and HMBG1 concentrations paralleled Calreticulin externalization. Search of literature revealed that active concentration of L-OHP was 38.0 ± 5.9 microM after a 1 hour isolated liver perfusion (ILP) which fits well with the intratumoral dose used in preclinical studies. Since L-OHP has active metabolites of mono- and dichloro DACH platin and diaquo DACH platin that are active for only 4 hours before being inactivated by conjugation and protein binding, AUC's were compared for ILP and systemic administration of L-OHP at 85 and 130 mg/m2, the FDA approved doses. AUC for ILP was 16.2 microg/ml (41 microM) of L-OHP at 1 hour and active moieties compared to 0.0003 (0.0008 microM) and 0.0193 microg/ml (0.049 microM) for 85 and 130 mg/m2 administered systemically, respectively. If hepatic clearance is equal, systemic administration of L-OHP would need to be increased by more than 100-fold to achieve an intratumoral concentration that induces ICD to externalize Calreticulin in liver metastases.

Conclusion: L-OHP optimally stimulates ICD at 80 microM (32.8 microg/ml) in human CRC while lower and higher concentrations cause non-immunogenic apoptosis. Image-guided intratumoral injection into liver metastases in colorectal carcinoma patients will be required because systemic administration will not deliver enough active L-OHP to cause ICD.

Citation Format: John Milburn Jessup, Daniel D. Taub. Injection of oxaliplatin into liver metastases will be required to break immune suppression in colorectal carcinoma patients [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 966.