On October 6, 2018 Loxo Oncology, Inc. (Nasdaq: LOXO), a biopharmaceutical company developing highly selective medicines for patients with genomically defined cancers, reported updated interim clinical data for LOXO-292 from the global Phase 1/2 LIBRETTO-001 trial in patients with RET-mutant medullary thyroid cancer (MTC) and RET fusion-positive thyroid cancer who were initially included in the LOXO-292 presentation at the 2018 ASCO (Free ASCO Whitepaper) Annual Meeting (Press release, Loxo Oncology, OCT 6, 2018, View Source [SID1234529804]). In these 38 patients, approximately 3.5 months of additional patient follow-up were available, as were first follow-up scans for the nine patients most recently enrolled. Sixteen of 17 (94%) responding RET-mutant MTC patients remained on therapy, with median follow-up of 8.4 months. Seven of seven (100%) responding RET fusion-positive thyroid cancer patients remained on therapy, with median follow-up of 8.5 months. Inclusion of new restaging data for the most recently enrolled patients resulted in a 59% overall response rate (56% confirmed overall response rate) in the presented subset of RET-mutant MTC patients, and a 78% confirmed overall response rate in the presented subset of RET fusion-positive thyroid cancer patients. These data are being presented today at the 88th Annual Meeting of the American Thyroid Association.

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"I am very pleased to present the latest LOXO-292 clinical data to colleagues at ATA, demonstrating the activity and safety profile of this promising new agent for RET-altered thyroid cancers," said Lori J. Wirth, M.D., associate professor of medicine at Harvard Medical School and Massachusetts General Hospital. "In the months since ASCO (Free ASCO Whitepaper) we continue to see encouraging early evidence that LOXO-292 has the potential to provide durable responses in heavily pre-treated patients with RET-driven cancers, with a promising safety profile at the Phase 2 dose of 160 mg BID. RET has been a known oncogene in thyroid cancer for many years and I am hopeful that these LOXO-292 data can further increase the awareness of this important target and, with Breakthrough Therapy Designation in hand, that the clinical program will quickly advance to reach our patients in need. "

Trial Background

LIBRETTO-001 is a Phase 1/2 trial of LOXO-292 in advanced cancer patients who primarily have activating RET alterations. LIBRETTO-001 contains a Phase 1 dose escalation phase and a Phase 2 dose expansion phase. The primary endpoint of the Phase 1 is the determination of the maximum tolerated dose (MTD) or recommended dose for further study. Secondary endpoints include safety, overall response rate (by RECIST 1.1) and duration of response. Initial clinical data were first reported at the 2018 American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) Annual Meeting.

Key Data Presented

The data presented today were based on a July 19, 2018 data cut-off date and included the 29 patients with RET-mutant MTC and the nine patients with RET fusion-positive thyroid cancer who were initially included in the LOXO-292 presentation at the 2018 ASCO (Free ASCO Whitepaper) Annual Meeting.

Patients were heavily pretreated, having received a median of three prior systemic treatment regimens. Of the patients with RET-mutant MTC, 79% had previously received cabozantinib or vandetanib and 45% had received prior treatment with both agents. Of the patients with RET fusion-positive thyroid cancer, 78% had previously received radioactive iodine and 78% had previously received sorafenib or lenvatinib.

With 3.5 months of additional follow-up since the 2018 ASCO (Free ASCO Whitepaper) Annual Meeting presentation, LOXO-292 demonstrated encouraging, early evidence of durable activity. Sixteen of 17 (94%) responding RET-mutant MTC patients remained on therapy and in response (median follow-up of 7.6 months for all 29 patients; median follow-up of 8.4 months for responding patients). Seven of seven (100%) responding RET fusion-positive thyroid remained on therapy and in response (median follow-up of 7.6 months for all nine patients; median follow-up of 8.5 months for responding patients). The longest treated patient was the first RET-mutant MTC patient enrolled, who had been on therapy for more than 13 months as of the data cut-off date.

The new data cutoff date allowed for the inclusion of first follow-up scans for nine patients (seven with RET-mutant MTC and two with RET fusion-positive thyroid cancer) who had not had any post-baseline response assessment as of the ASCO (Free ASCO Whitepaper) presentation. Of 29 patients with RET-mutant MTC, 17 demonstrated an objective response by RECIST 1.1 (two complete responses and 15 partial responses, including two patients with unconfirmed partial responses awaiting confirmatory response assessments) and seven additional patients demonstrated evidence of tumor regression (-12% to -26%). The overall response rate was 59% (17/29) (95% CI: 39%-77%) and the confirmed overall response rate was 56% (15/27) (95% CI: 35%-75%). Included in this analysis are two patients with non-measurable disease at baseline (1 confirmed complete response, 1 stable disease). Of nine patients with RET fusion-positive thyroid cancer, seven demonstrated an objective response by RECIST 1.1 (all partial responses) and one additional patient demonstrated evidence of tumor regression (-21%). The confirmed overall response rate was 78% (7/9) (95% CI: 40%-97%). Included in the analysis is one patient with non-measurable disease at baseline (stable disease). Response assessments were performed by the local clinical trial sites.

Anti-tumor activity was observed regardless of RET mutation, RET fusion partner, and prior multikinase inhibitor treatment. One patient, with RET fusion-positive thyroid cancer, had RECIST target lesions in the central nervous system (CNS) and exhibited an intracranial partial response by RECIST 1.1, pending confirmation.

Of the 82 patients in the safety analysis, most treatment-emergent adverse events were Grade 1 in severity and judged by the investigator as not related to LOXO-292. The treatment-emergent adverse events observed in ≥10% of patients, regardless of relationship to LOXO-292, were diarrhea (15% Grade 1, 7% Grade 2, 1% Grade 3), fatigue (9% Grade 1, 13% Grade 2, 0% ≥Grade 3), dry mouth (21% Grade 1, 0% ≥Grade 2), constipation (17% Grade 1, 2% Grade 2, 0% ≥Grade 3), hypomagnesemia (12% Grade 1, 1% Grade 2, 0% ≥Grade 3), cough (11% Grade 1, 1% Grade 2, 0% ≥Grade 3), headache (10% Grade 1, 1% Grade 2, 1% Grade 3) and nausea (9% Grade 1, 4% Grade 2, 0% ≥Grade 3). Four patients experienced adverse events ≥Grade 3 that were attributed to LOXO-292 (all Grade 3): tumor lysis syndrome, increased ALT/AST, diarrhea, and thrombocytopenia. All resolved with dose interruption. 160mg BID has been advanced as the Phase 2 dose, with dose exploration at 200mg BID ongoing to further characterize LOXO-292 safety and efficacy.

The presentation will be available online at View Source

About LOXO-292
LOXO-292 is an oral and selective investigational new drug in clinical development for the treatment of patients with cancers that harbor abnormalities in the rearranged during transfection (RET) kinase. RET fusions and mutations occur across multiple tumor types with varying frequency. LOXO-292 was designed to inhibit native RET signaling as well as anticipated acquired resistance mechanisms that could otherwise limit the activity of this therapeutic approach. LOXO-292 has been granted Breakthrough Therapy Designation by the U.S. FDA.

LOXO-292 is currently being studied in the global LIBRETTO-001 Phase 1/2 trial. For additional information about the LOXO-292 clinical trial, please refer to www.clinicaltrials.gov. Interested patients and physicians can contact the Loxo Oncology Physician and Patient RET Clinical Trial Hotline at 1-855-RET-4-292 or email [email protected].

About RET-Altered Cancers
Genomic alterations in RET kinase, which include fusions and activating point mutations, lead to overactive RET signaling and uncontrolled cell growth. RET fusions have been identified in approximately 2% of non-small cell lung cancer, 10-20% of papillary and other thyroid cancers, and a subset of other cancers. Activating RET point mutations account for approximately 60% of medullary thyroid cancer (MTC). Both RET fusion cancers and RET-mutant MTC are primarily dependent on this single activated kinase for their proliferation and survival. This dependency, often referred to as "oncogene addiction," renders such tumors highly susceptible to small molecule inhibitors targeting RET.