Evaluation of SN-38 PK profile in patients with RAS wild-type metastatic colorectal cancer treated with a combination of SCO-101 and FOLFIRI.

Abstract

185 Background: The FOLFIRI regimen (5-fluorouracil, leucovorin and irinotecan) is a predominant treatment regimen for metastatic colorectal cancer. To optimize the benefit for the patients, it would be desirable to increase the efficacy of irinotecan by increasing the exposure of SN-38 (the active metabolite of irinotecan) to the cancer cells, while maintaining a good safety profile. The oral drug SCO-101, that is currently being developed by Scandion Oncology A/S, was tested in an early clinical trial (CORIST-trial, ClinicalTrials.gov identifier: NCT04247256). SCO-101 is an inhibitor of ABCG2, UGT1A1 and SRPK1. The CORIST trial was set up to address the safety, tolerability, and efficacy of SCO-101 given orally for 6 days followed by FOLFIRI at varying doses from day 5 to 7, in a biweekly schedule, in patients with metastatic colorectal cancer who have formerly been treated with FOLFIRI and afterwards progressed. The first part of the study was a dose-finding study, where the impact of SCO-101 on the pharmacokinetics (PK) of SN-38 was studied. Methods: 12 patients from the dose-finding part of the CORIST study received 150 mg SCO-101 for 6 days and 45 – 80% of the recommended dose of FOLFIRI. 6 of the patients had RAS wild-type tumors and these patients are the subject of the current analysis. Blood for PK analysis was sampled from the patients at 1, 2, 4, 8, 24, 48, and 96 hours after treatment with FOLFIRI and SCO-101. The blood samples were analyzed for Cmax, T½ and AUC (0-24h) of SCO-101, irinotecan and SN-38. Results: The PK of SN-38 from the patients in the study, normalized to a dose of irinotecan of 90 mg/m2 showed a T½ day 5 of 19 hours (SD 5,7) a Cmax of 60 ng/ml (SD 20,6) and an AUC_0-24h of 1415 hxng/ml (SD: 670). The results were compared to SN-38 data from treatment with irinotecan at 180 mg/m2, which is used in standard doses of FOLFIRI and the data is presented in the table. The data analysis showed an increased T½, increased Cmax and increased AUC of SN-38 when combining SCO-101 with 90 mg/m2 irinotecan, compared to SN-38 PK data from standard irinotecan treatment of 180 mg/m2. The toxicity profile of the patients treated with 90 mg irinotecan/m2 (50% FOLFIRI) showed only grade 1 and 2 adverse events. Conclusions: SCO-101 in combination with FOLFIRI has demonstrated the ability to modulate the PK profile of SN-38 in mCRC patients with RAS wild-type tumors, by significantly increasing the half-life, the peak plasma concentration, and area under the curve of SN-38. The combined treatment was well tolerated, and the drug is now being tested for efficacy in the CORIST trial.[Table: see text]