American Association for Cancer Research
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Supplementary Figure S1 from XTX301, a Tumor-Activated Interleukin-12 Has the Potential to Widen the Therapeutic Index of IL12 Treatment for Solid Tumors as Evidenced by Preclinical Studies

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journal contribution
posted on 2024-04-04, 15:20 authored by Ekta Patel, Natalia V. Malkova, David Crowe, Magali Pederzoli-Ribeil, Damiano Fantini, Manoussa Fanny, Hanumantha Rao Madala, Kurt A. Jenkins, Oleg Yerov, Justin Greene, Wilson Guzman, Caitlin O'Toole, Jacob Taylor, Rebekah K. O'Donnell, Parker Johnson, Bernard B. Lanter, Brian Ames, Jia Chen, Sallyann Vu, Hsin-Jung Wu, Susan Cantin, Megan McLaughlin, Yu-Shan S. Hsiao, Dheeraj S. Tomar, Raphael Rozenfeld, Lakshmanan Thiruneelakantapillai, Ronan C. O'Hagan, Benjamin Nicholson, Jennifer O'Neil, Carl Uli Bialucha

Supplemental Figure S1: A representative triplex fluorescent western blot image showing cleavage of XTX301 in primary human tumor specimens. Antibodies against human IL-12 (Green), human IL-12Rβ2 (Red) and human IgG (Blue) were used, a merged image is shown in the figure. The 145 Kda band is the intact XTX301 or non-cleavable construct, the 85Kda band is the cleaved XTX301/unmasked construct, the green arrow indicates free IL-12 released upon cleavage of XTX301. The % of cleavage mXT301 refers to the percentage of cleaved molecule compared to the total (intact and cleaved) molecule detected by western blot using the IL-12Rβ2 signal.





IL12 is a proinflammatory cytokine, that has shown promising antitumor activity in humans by promoting the recruitment and activation of immune cells in tumors. However, the systemic administration of IL12 has been accompanied by considerable toxicity, prompting interest in researching alternatives to drive preferential IL12 bioactivity in the tumor. Here, we have generated XTX301, a tumor-activated IL12 linked to the human Fc protein via a protease cleavable linker that is pharmacologically inactivated by an IL12 receptor subunit beta 2 masking domain. In vitro characterization demonstrates multiple matrix metalloproteases, as well as human primary tumors cultured as cell suspensions, can effectively activate XTX301. Intravenous administration of a mouse surrogate mXTX301 demonstrated significant tumor growth inhibition (TGI) in inflamed and non-inflamed mouse models without causing systemic toxicities. The superiority of mXTX301 in mediating TGI compared with non-activatable control molecules and the greater percentage of active mXTX301 in tumors versus other organs further confirms activation by the tumor microenvironment–associated proteases in vivo. Pharmacodynamic characterization shows tumor selective increases in inflammation and upregulation of immune-related genes involved in IFNγ cell signaling, antigen processing, presentation, and adaptive immune response. XTX301 was tolerated following four repeat doses up to 2.0 mg/kg in a nonhuman primate study; XTX301 exposures were substantially higher than those at the minimally efficacious dose in mice. Thus, XTX301 has the potential to achieve potent antitumor activity while widening the therapeutic index of IL12 treatment and is currently being evaluated in a phase I clinical trial.