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LTX-315 sequentially promotes lymphocyte-independent and lymphocyte-dependent antitumor effects
Hsin-Wei Liao1,2, Christopher Garris1,2, Christina Pfirschke1
1Center for Systems Biology, Massachusetts General Hospital Research Institute, Harvard Medical School, Boston, MA, USA.
Abstract:
LTX-315 is an oncolytic peptide that has antitumor efficacy in mice grafted with various tumor cell lines and is currently being tested in phase II clinical trials. Here we aimed to further evaluate LTX-315 in conditional genetic mouse models of cancer that typically resist current treatment options and to better understand the drug's mode of action in vivo. We report LTX-315 mediates profound antitumor effects against Braf- and Pten-driven melanoma and delays the progression of Kras- and P53-driven soft tissue sarcoma in mice. Additionally, we show in melanoma that LTX-315 triggers two sequential phases of antitumor response. The first phase of response, which begins within minutes of drug delivery into tumors, is defined by disrupted tumor vasculature and decreased tumor burden and occurs independently of lymphocytes. The second phase of response, which continues over weeks, is defined by long-term alteration of the tumor microenvironment; the changes induced by LTX-315 are most notably characterized by CD8+ T cell infiltration. We further show that these CD8+ T cells are involved in suppressing melanoma outgrowth in mice and report similar CD8+ T cell infiltration following LTX-315 treatment in melanoma and sarcoma patients. Taken together, these findings reveal LTX-315's multiple antitumor effects, including disrupting the tumor vasculature and promoting the conversion of poorly immunogenic tumors into ones that display antitumor T cell immunity.
Insights
LTX-315, an oncolytic peptide, shows significant antitumor effects in mouse cancer models by disrupting tumor blood vessels and recruiting CD8+ T cells. This peptide therapy holds promise for treating resistant cancers.
Area of Science:
- Oncology
- Immunology
- Pharmacology
Background:
- LTX-315 is an oncolytic peptide with demonstrated antitumor efficacy.
- It is currently undergoing Phase II clinical trials.
- Understanding its mechanism in treatment-resistant cancers is crucial.
Purpose of the Study:
- Evaluate LTX-315 in genetic mouse models of resistant cancers.
- Elucidate the in vivo mechanism of action of LTX-315.
- Assess LTX-315's impact on tumor vasculature and immune microenvironment.
Main Methods:
- Utilized conditional genetic mouse models for melanoma and soft tissue sarcoma.
- Administered LTX-315 directly into tumors.
- Analyzed tumor vasculature, burden, and immune cell infiltration (CD8+ T cells).
Main Results:
- LTX-315 demonstrated significant antitumor effects in Braf- and Pten-driven melanoma.
- It delayed progression in Kras- and P53-driven soft tissue sarcoma.
- Two distinct phases of antitumor response were observed: initial vascular disruption and later CD8+ T cell infiltration.
Conclusions:
- LTX-315 exhibits potent antitumor activity through dual mechanisms: vascular disruption and immune modulation.
- The drug converts poorly immunogenic tumors into ones that elicit anti-tumor T cell immunity.
- Findings support LTX-315's potential in treating resistant cancers and highlight its role in enhancing anti-tumor T cell responses.