On June 22, 2020 Turning Point Therapeutics, Inc. (NASDAQ: TPTX), a precision oncology company developing next-generation therapies that target genetic drivers of cancer, reported preclinical studies highlighting the potential for its lead drug candidate, repotrectinib, to increase the effectiveness of KRAS-G12C and MEK inhibitors in cancer models, and for its next-generation ALK inhibitor candidate, TPX-0131, to overcome ALK-resistant mutations (Press release, Turning Point Therapeutics, JUN 22, 2020, View Source [SID1234564369]).

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The studies were included as part of three poster presentations at today’s virtual annual meeting of the American Association for Cancer Research (AACR) (Free AACR Whitepaper).

"Feedback reactivation and bypass signaling may limit the efficacy of KRAS-G12C and MEK inhibitors against KRAS-driven tumors, and our encouraging preclinical data shows how repotrectinib has the potential to increase the anti-tumor effects by inhibiting SRC, FAK and JAK2 signaling," said Athena Countouriotis, M.D., president and chief executive officer. "We look forward to building upon these preclinical combination studies as we explore the potential for repotrectinib to address a broad set of oncogenic-driven solid tumors.

"In addition, we are excited to share for the first time preclinical data for our fourth drug candidate, TPX-0131, a next generation ALK inhibitor in IND enabling studies. We are encouraged by TPX-0131’s preclinical potency against both wildtype ALK and the most common resistant mutations."

Jessica Lin, M.D., Attending Physician in the Center for Thoracic Cancers at Massachusetts General Hospital Cancer Center and Henri and Belinda Termeer Center for Targeted Therapies, and Instructor in Medicine at Harvard Medical School said: "Resistant mutations following treatment with approved ALK inhibitors remain a challenge for patients, especially the difficult to treat G1202R/del solvent front mutation which can occur in up to 42 percent of patients who develop a resistance mutation, and compound mutations that develop after the recently approved agent Lorbrena. The preclinical potency of TPX-0131 against these mutations suggests that it warrants further study."

Repotrectinib Combination Studies
The preclinical antitumor activities of repotrectinib in combination with proxy molecules for AMG510, an investigational KRAS-G12C inhibitor, and trametinib, an approved MEK inhibitor were highlighted for the first time in two poster presentations. The studies show repotrectinib’s inhibition of SRC, FAK and JAK2 at therapeutically relevant concentrations, which in combination with AMG510 or trametinib demonstrated a synergistic effect over the single agent by reducing tumor cell growth and enhancing tumor cell death. The repotrectinib-trametinib combination studies were replicated across panels of KRAS mutant non-small cell lung, colorectal and pancreatic cancer cell lines that harbor a spectrum of KRAS mutations.

The frequently mutated Kirsten Rat Sarcoma (KRAS) viral oncogene is associated with a broad range of human cancers, including approximately 25 percent of non-small cell lung, 45 percent of colorectal and 75 percent of pancreatic cancers. Therapeutic targeting of KRAS has proven challenging, in part due to resistance and adaptive upregulation of alternative signaling pathways that promote tumor cell survival, as well as concurrent secretion of various cytokines and growth factors.

In preclinical models, repotrectinib inhibits SRC and FAK signaling, a key pathway for oncogenic resistance, and JAK2, a driver of cytokine secretion pathways.

TPX-0131, a Next-Generation ALK Inhibitor
TPX-0131 has been internally designed with a compact macrocyclic structure to bind completely within the ATP binding site of ALK. In preclinical studies, TPX-0131 potently inhibits wildtype ALK and numerous ALK mutations, in particular the clinically observed G1202R solvent-front mutation and G1202R/L1196M compound mutation.

In cell proliferation assays presented at AACR (Free AACR Whitepaper), TPX-0131 exhibited greater potency against wildtype ALK as compared to proxy molecules for approved front-line ALK inhibitors crizotinib, alectinib, brigatinib and ceritinib, and comparable potency to a proxy molecule for approved ALK inhibitor, lorlatinib. TPX-0131 demonstrated more than 100-fold greater potency against the G1202R solvent-front mutation as compared to proxy molecules for the approved ALK inhibitors. Additionally, TPX-0131 is the most potent inhibitor against a range of EML4-ALK compound mutations while prior generation ALK inhibitors tested have shown moderate to no activity.

Anaplastic lymphoma kinase- (ALK) driven tumors are estimated to represent up to 7 percent of driver oncogenes in non-small cell lung cancer and in one study of patients who develop a resistance mutation, G1202R was reported in approximately 42 percent of patients, and compound mutations have been reported in approximately 35 percent of patients who developed resistance following treatment with lorlatinib.

The three posters presented today are:

Title: Repotrectinib increases effectiveness of KRAS-G12C inhibitors in KRAS-G12C mutant cancer models via simultaneous SRC/FAK/JAK2 inhibition
Abstract Number: 1958

Title: Repotrectinib increases effectiveness of MEK inhibitor trametinib in KRAS mutant cancer models via simultaneous SRC/FAK/JAK2 inhibition
Abstract Number: 1957

Title: TPX-0131: A next generation macrocyclic ALK inhibitor that overcomes ALK resistant mutations refractory to current approved ALK inhibitorsbstract Number: 5226