Osimertinib and Selpercatinib Efficacy, Safety, and Resistance in a Multicenter, Prospectively Treated Cohort of EGFR-Mutant and RET Fusion-Positive Lung Cancers

PURPOSE

Acquired RET fusions have been reported at resistance to treatment with EGFR inhibitors in EGFR-mutant non-small cell lung cancer (NSCLC); however, a multicenter cohort of patients with EGFR-mutant lung cancers treated with osimertinib and selpercatinib for RET fusion-mediated osimertinib resistance has not previously been published.

PATIENTS AND METHODS

Patients who received selpercatinib in combination with osimertinib on a prospective expanded access clinical trial (NCT03906331) and single-patient compassionate use programs across five countries were centrally analyzed. All patients had advanced EGFR-mutant NSCLC with a RET fusion detected from tissue or plasma following osimertinib therapy. Clinicopathologic and outcomes data were collected.

RESULTS

Fourteen patients with EGFR-mutant and RET fusion-positive lung cancers who experienced prior progression on osimertinib received osimertinib and selpercatinib. EGFR exon 19 deletions (±T790M, 86%) and non-KIF5B fusions (CCDC6-RET 50%, NCOA4-RET 36%) predominated. Osimertinib 80 mg daily and selpercatinib 80 mg twice daily were the most commonly administered dosages. The response rate, disease control rate, and median treatment duration were 50% [95% confidence interval (CI), 25%-75%, n = 12], 83% (95% CI, 55%-95%), and 7.9 months (range, 0.8-25+), respectively. Resistance was complex, involving EGFR on-target (EGFR C797S), RET on-target (RET G810S), and off-target (EML4-ALK/STRN-ALK, KRAS G12S, BRAF V600E) mechanisms; RET fusion loss; or polyclonal mechanisms.

CONCLUSIONS

For patients with EGFR-mutant NSCLC with an acquired RET fusion as a mechanism of EGFR inhibitor resistance, the addition of selpercatinib to osimertinib was feasible and safe and offered clinical benefit, supporting the prospective evaluation of this combination. See related commentary by Krebs and Popat, p. 2951.

A phase I study of LY3410738, a first-in-class covalent inhibitor of mutant IDH1 in cholangiocarcinoma and other advanced solid tumors

TPS350

Background: Mutations in isocitrate dehydrogenase 1 (mIDH1) are found in approximately 20-30% of patients with intrahepatic cholangiocarcinoma (CCA), and less commonly in glioma, chondrosarcoma, and other gastrointestinal malignancies. Despite documented clinical activity of mIDH1 inhibition in solid tumors, there are no approved targeted therapies for this patient population. LY3410738 is a potent, selective, and covalent inhibitor of mIDH1 R132. LY3410738 is differentiated from prior mIDH1 inhibitors by 1) its unique covalent binding mode, 2) its increased potency, and 3) its unique binding site outside of the dimer interface, which enables activity in the setting of known common second-site IDH1 mutations. Methods: This is an open-label, multicenter, global phase 1 study with oral LY3410738 currently enrolling patients with advanced CCA and other solid tumor types (NCT04521686). A dose escalation cohort will be followed with 4 exploratory expansion cohorts. The primary objective for dose escalation is determination of the maximum tolerated dose (MTD)/recommended phase 2 dose (RP2D). The primary objective for dose expansion is to assess the preliminary anti-tumor activity by ORR of LY3410738 when administered alone or in combination with cisplatin plus gemcitabine. Secondary objectives include evaluating safety and tolerability, pharmacokinetics, pharmacodynamics, progression free survival, and overall survival. Key inclusion criteria include any solid tumor with the presence of mIDH1 R132, ECOG performance status ≤1, and adequate organ function. Any prior treatment including an IDH1 inhibitor is allowed in the dose escalation cohort. Exclusion criteria include presence of active central nervous system metastases, leptomeningeal disease, and active or uncontrolled infection. CCA patients must not have had locoregional therapy within 4 weeks prior to the initial study dose, history of hepatic encephalopathy or refractory ascites, ongoing cholangitis, or mixed hepatocellular-CCA histology. Dose escalation will follow a 3+3 design and will allow patient back-fill to dose levels previously cleared for safety. Each cycle will be 28 days (4 weeks). Once the RP2D is determined, LY3410738 will be evaluated as monotherapy in expansion cohorts 1-3, and in combination with cisplatin plus gemcitabine in expansion cohort 4. Cohort 1 will enroll CCA patients with measurable disease who have received prior chemotherapy. Cohort 2 will enroll patients with advanced solid tumors except CCA who have measurable disease and received standard therapies. Cohort 3 will enroll patients with advanced solid tumors who have non-measurable disease and received standard therapies. Cohort 4 will enroll CCA patients with measurable disease who are treatment naïve for advanced disease. Clinical trial information: NCT04521686.

Rapid, complete and sustained tumour response to the TRK inhibitor larotrectinib in an infant with recurrent, chemotherapy-refractory infantile fibrosarcoma carrying the characteristic ETV6-NTRK3 gene fusion

BACKGROUND

The ETV6-NTRK3 gene fusion is present in the majority of cases of infantile fibrosarcoma (IFS) and acts as a potent oncogenic driver. We report the very rapid, complete, and sustained response of an advanced, chemotherapy-refractory, recurrent IFS to targeted treatment with the oral tropomyosin receptor kinase (TRK) inhibitor larotrectinib.

PATIENT AND METHODS

A male infant born with a large congenital IFS of the tongue had the tumour surgically resected at age 4 days. Within 2 months, he developed extensive lymph node recurrence that progressed during two cycles of vincristine-doxorubicin-cyclophosphamide chemotherapy. At screening, a large right cervical mass was clinically visible. Magnetic resonance imaging (MRI) revealed bilateral cervical and axillary lymph node involvement as well as infiltration of the floor of the mouth. The largest lesion measured 5.5×4.5×4.4 cm (ca. 55 cm3). The patient started outpatient oral larotrectinib at 20 mg/kg twice daily at age 3.5 months.

RESULTS

After 4 days on treatment, the parents noted that the index tumour was visibly smaller and softer. The rapid tumour regression continued over the following weeks. On day 56 of treatment, the first scheduled control MRI showed the target lesion had shrunk to 1.2×1.2×0.8 cm (ca. 0.6 cm3), corresponding to a complete response according to the Response Evaluation Criteria In Solid Tumors version 1.1. This response was maintained over subsequent follow-up visits, and on day 112 at the second control MRI the target lymph node was completely normal. At last follow-up, the disease remained in complete remission after 16 months on larotrectinib, with negligible toxicity and no safety concerns.

CONCLUSION(S)

Selective TRK inhibition by larotrectinib offers a novel, highly specific and highly effective therapeutic option for IFS carrying the characteristic ETV6-NTRK3 gene fusion. Its use should be considered when surgery is not feasible. (NCT02637687).

Pharmacokinetics of tacrolimus co-administered with adefovir dipivoxil to liver transplant recipients

BACKGROUND

Adefovir dipivoxil has activity against wild-type and lamivudine-resistant hepatitis B virus (HBV) and is frequently used to manage HBV infection in transplant recipients. Calcineurin inhibitors are a central component of immunosuppressive therapy.

AIMS

Study GS-02-531 was an open-label, multicentre drug interaction trial to examine potential drug interactions between adefovir and tacrolimus in stable post-transplant recipients.

MATERIALS AND METHODS

Sixteen non-HBV-infected post-transplant recipients with median age 45.5 years (69% male, 44% Caucasian, 50% Hispanic and 6% Black) and stable hepatic and renal function on a stable daily dose of tacrolimus (2-10 mg total daily dose) were studied before (tacrolimus alone) and after co-administration of adefovir 10 mg daily for 14 days (Days 1-14). Pharmacokinetic (PK) analyses utilized non-compartmental methods.

RESULTS

The median elimination half-life of tacrolimus was 14.47 and 12.59 h for Day 0 and Day 14 respectively. The geometric mean ratios for tacrolimus on Day 14 vs Day 0 were 105.2% [90% confidence interval (90% CI): 89.8-123%] for C(max) and 106.4% (90% CI: 92.9-122%) for AUC(tau). Both 90% CIs for the ratios were contained within the predefined lack of interaction bounds of 80 and 125% (i.e. within the bounds for the equivalence assessment), indicating that these PK parameters of tacrolimus are not significantly altered by co-administration of adefovir. Similarly, the observed adefovir PK parameters after 14 days of co-administration with tacrolimus were comparable to historical data in non-transplant patients receiving adefovir alone. Serum creatinine values were stable during the study period.

CONCLUSION

There is no significant PK interaction between tacrolimus and adefovir co-administered to liver transplant recipients for 14 days.