Abstract 4048: New approach to target metastatic colorectal cancer organotropism with L-Annamycin
Authors: Zielinski Rafal J. , Grela Krzysztof Grela , Cardenas-Zuniga Roberto , Skora Stanislaw , Fokt Izabela , Felix Edward , Grybowski Damian , Priebe Waldemar 
Published: June 2022

Colorectal cancer (CRC) is a frequently occurring disease and the second most common cause of cancer deaths when men and women are combined. CRC metastasis is strongly associated with mortality. The liver and lungs are the most frequent sites of distant disease, accounting for ~70% and ~12% of cases, respectively. We hypothesize that anticancer agents that mimic the organotropism of metastatic CRC will be highly effective in treating CRC patients. Our studies have identified that Annamycin (ANN), a potent topoisomerase II poison that displays organotropism imitating that of metastatic CRC. ANN is an analog of doxorubicin (Dox) that shows unique properties. Notably, ANN is active against multidrug-resistant tumors and undergoes efficient uptake by lungs and liver. ANN is easily formulated in multilamellar liposomes (L-ANN), which further increases ANN levels in lungs and liver.

Objective. The objective of this study was to assess the efficacy of L-ANN in experimental CRC liver and lung metastasis models.

Methods. The efficacy of L-ANN was tested in syngeneic models of metastatic CRC established in lungs or liver. For lung metastasis model, CT26-Luc cells were injected intravenously (IV) into Balb/c mice, followed by weekly IV treatment of L-ANN (4 and 6 mg/kg). The liver metastatic model was established using intrasplenic injection protocol. Mice received six weekly IV injections of 4 mg/kg of L-ANN or vehicle. Bioluminescent imaging (BLI), Magnetic Resonance Imaging (MRI) or Computer Tomography (CT) were used to track tumor progression.

Results. L-ANN exhibited robust antitumor activity in both models. In the lung metastasis model, a dose-dependent delay in the tumor progression was visualized by both BLI and CT scan in the L-ANN treated group. The delay correlated with 272% extension of survival in the group receiving 6 mg/kg L-ANN [median survival (MS) 79d for treated vs 29d vehicle, p&lt;0.0001] and 234% for the animals dosed with L-ANN at 4 mg/kg [MS 68d, p=0.0012]. In the liver metastasis model, all vehicle-treated mice showed massive tumors in the liver and peritoneal cavity as monitored by BLI and MRI. In the vehicle group, 13/14 died or were euthanized by 35d (median survival was 34.5d). Yet, no tumors were detected by BLI or MRI in L-ANN treated mice as of 44d and 0/14 mice died (100% survival). This indicates a highly significant (P&lt; 0.0001) extension of survival (ongoing experiment).

Conclusion. In summary, the strategy to develop anticancer agents that imitate metastatic CRC organotropism appears to be highly promising and is supported by these results. Our previous in vivo studies of L-ANN in sarcoma lung metastasis models already led to initiation of multicenter clinical studies (NCT04887298). This study demonstrating L-ANN efficacy in CRC models provides convincing evidence for further preclinical development aimed at initiation of clinical studies in CRC metastatic patients.

Citation Format: Rafal J. Zielinski, Krzysztof Grela Grela, Roberto Cardenas-Zuniga, Stanislaw Skora, Izabela Fokt, Edward Felix, Damian Grybowski, Waldemar Priebe. New approach to target metastatic colorectal cancer organotropism with L-Annamycin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4048.