Date: 2017-06-03
Type of information: Presentation of results at a congress
phase: 2
Announcement: presentation of results at the American Society of Clinical Oncology (ASCO) annual meeting, in Chicago
Company: Loxo Oncology (USA - CT)
Product: LOXO- 101 (larotrectinib - (S)-N-(5-((R)-2-(2,5-difluorophenyl)pyrrolidin-1-yl)pyrazolo[1,5-a]pyrimidin-3-yl)-3-hydroxypyrrolidine-1-carboxamide hydrogen sulfate
Action mechanism: enzyme inhibitor/kinase inhibitor/TRK inhibitor. LOXO-101 is a potent, oral, selective inhibitor of tropomyosin receptor kinase (TRK) signaling molecules. The TRK family (TRKA, TRKB, and TRKC) has been implicated in diverse tumor types such as lung cancer, head and neck cancer, melanoma, colorectal cancer, sarcoma, and breast cancer. LOXO-101 was built specifically to inhibit TRK and is currently being evaluated in a Phase 1 dose escalation trial for patients with advanced solid tumors. LOXO-101 was developed in collaboration with Array BioPharma.
Disease: NTRK fusion-positive tumors
Therapeutic area: Cancer - Oncology
Country: Denmark, Ireland, Republic of Korea, Singapore, Spain, USA
Trial details: The Phase 2 NAVIGATE clinical trial is a global, multi-center, single-arm, open-label basket trial in adult patients with solid tumors that harbor a TRK fusion, as determined by any Clinical Laboratory Improvement Amendments (CLIA) certified or equivalently-accredited test, the choice of which will be guided by the treating physician's routine clinical laboratory practice. A basket trial is a new clinical trial design that enrolls patients based on a common, defining genetic feature of their cancer, rather than based on an anatomic definition. LOXO-101 is administered orally as a single agent at 100 mg twice-daily continuously in 28-day cycles. This dose has been shown to achieve systemic drug exposures anticipated to inhibit TRK signaling by over 90%. The primary endpoint of the trial is the overall response rate (ORR) to LOXO-101, as measured by the proportion of subjects with best overall confirmed response of complete response or partial response by the Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST 1.1), or Response Assessment in Neuro-Oncology (RANO) criteria, as appropriate. Secondary endpoints include duration of response, the proportion of subjects that have any tumor regression as a best response, progression-free survival, overall survival, safety and tolerability. (NCT02576431)
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* Includes unconfirmed responses with confirmatory scans pending (4 PR, 1 CR). All patients with unconfirmed responses remain in response and ongoing on study.
As shown in the above table, the confirmed ORR is 76 percent in 50 patients for whom follow-up was sufficiently long to include a confirmatory scan. The ORR is 78 percent when an additional 5 patients, recently enrolled, with unconfirmed PR (n=4) and CR (n=1), are included. ORR was generally consistent across tumor types, TRK gene fusions, and various diagnostic tests. In the pediatric setting, larotrectinib showed promising activity in the pre-surgical management of patients with infantile fibrosarcoma, with 3 patients treated to best response, which allowed for subsequent referral to surgery with curative intent.
Median DOR and PFS have not been reached. Ninety-three percent of all responding patients either remain on drug or received surgery with curative intent. Seventy-five percent of all patients enrolled either remain on drug or received surgery with curative intent.
The safety data presented at ASCO encompass the entire larotrectinib safety database in cancer patients (n=125) intended to support an NDA. The most common treatment-emergent adverse events, regardless of relationship to larotrectinib, included fatigue (15% Grade 1, 18% Grade 2, 5% Grade 3), dizziness (22% Grade 1, 4% Grade 2, 2% Grade 3), nausea (20% Grade 1, 5% Grade 2, 2% Grade 3), and anemia (8% Grade 1, 9% Grade 2, 9% Grade 3). Seven (13%) of patients required a dose reduction due to an adverse event. Of note, all patients requiring dose reduction experienced tumor regression (1 CR, 5 PR, 1 SD), which has continued on the reduced dose. Nearly all of the dose reductions were due to infrequent neurocognitive adverse events, likely a result of on-target TRK inhibition in the CNS. No patients discontinued larotrectinib due to an adverse event.
Six patients responded to larotrectinib but subsequently progressed, a pattern referred to as “acquired resistance.” Progression biopsies from five of six patients indicate a consistent mechanism of acquired resistance, namely a solvent front mutation. A solvent front mutation is an amino acid substitution in a kinase that reduces the binding potency of a targeted drug. In the case of NTRK1 and NTRK3, these solvent front amino acid substitutions are denoted as G595R and G623R, respectively. The presence of an acquired resistance mutation in a primary activating oncogene suggests that the involved cancer cell remains dependent on the aberrant signaling pathway that had been successfully drugged previously.
• On March 31, 2017, Loxo Oncology announced that larotrectinib (LOXO-101) data will be presented at the American Association for Cancer Research (AACR) 2017 Annual Meeting. The abstract and poster describe initial clinical data across the larotrectinib program for all patients with TRK fusion primary CNS cancers. The cases include three patients with glioblastoma: one patient treated under an expanded access protocol and two patients treated in the ongoing trial. In the cases described, larotrectinib showed preliminary evidence of anti-tumor activity. The expanded access patient had progressed through prior radiation, temozolomide and bevacizumab and demonstrated a brief mixed radiographic response on larotrectinib in the context of a molecularly complex tumor (select regions of the tumor harbored a TRK fusion, while others did not). The two patients treated in NAVIGATE, described in the poster, were enrolled following progression on chemoradiation and temozolomide (both cases) and bevacizumab (one case). The NAVIGATE patients remain on therapy at four months with radiographic evidence of treatment effect, as of a March 13, 2017 data cut-off date.
Enrolled Patients with Confirmatory Response Data Available (n=50)
All Enrolled Patients (n=55)*
Objective Response Rate
(ORR = PR+CR)
76%
(95% CI: 62% – 87%)
78%
(95% CI: 65% – 88%)
Partial Response (PR)
64%
65%*
Complete Response (CR)
12%
13%*
Stable Disease
12%
11%
Progressive Disease
12%
11%
