Project description:BackgroundRET mutations occur in 70% of medullary thyroid cancers, and RET fusions occur rarely in other thyroid cancers. In patients with RET-altered thyroid cancers, the efficacy and safety of selective RET inhibition are unknown.MethodsWe enrolled patients with RET-mutant medullary thyroid cancer with or without previous vandetanib or cabozantinib treatment, as well as those with previously treated RET fusion-positive thyroid cancer, in a phase 1-2 trial of selpercatinib. The primary end point was an objective response (a complete or partial response), as determined by an independent review committee. Secondary end points included the duration of response, progression-free survival, and safety.ResultsIn the first 55 consecutively enrolled patients with RET-mutant medullary thyroid cancer who had previously received vandetanib, cabozantinib, or both, the percentage who had a response was 69% (95% confidence interval [CI], 55 to 81), and 1-year progression-free survival was 82% (95% CI, 69 to 90). In 88 patients with RET-mutant medullary thyroid cancer who had not previously received vandetanib or cabozantinib, the percentage who had a response was 73% (95% CI, 62 to 82), and 1-year progression-free survival was 92% (95% CI, 82 to 97). In 19 patients with previously treated RET fusion-positive thyroid cancer, the percentage who had a response was 79% (95% CI, 54 to 94), and 1-year progression-free survival was 64% (95% CI, 37 to 82). The most common adverse events of grade 3 or higher were hypertension (in 21% of the patients), increased alanine aminotransferase level (in 11%), increased aspartate aminotransferase level (in 9%), hyponatremia (in 8%), and diarrhea (in 6%). Of all 531 patients treated, 12 (2%) discontinued selpercatinib owing to drug-related adverse events.ConclusionsIn this phase 1-2 trial, selpercatinib showed durable efficacy with mainly low-grade toxic effects in patients with medullary thyroid cancer with and without previous vandetanib or cabozantinib treatment. (Funded by Loxo Oncology and others; LIBRETTO-001 ClinicalTrials.gov number, NCT03157128.).
Project description:ContextMetastatic medullary thyroid carcinoma (MTC) and radioactive iodine-refractory differentiated thyroid carcinoma (RAI-R DTC) have poor prognosis and limited treatment options. Selpercatinib (LOXO-292), a selective kinase inhibitor targeting the RET gene, has shown a 69% to 79% objective response rate in this cohort with benefits in other tumors including lung cancer harboring the same oncogenic driver. Published reports describe only 17% of patients experiencing gastrointestinal (GI) adverse effects (AEs), which is in contrast to our local experience.ObjectiveHere we characterize the AEs and correlate them with radiological and histopathological findings.MethodsSequential patients enrolled in LIBRETTO-001 at Royal North Shore Hospital, Sydney, Australia, with available imaging (n = 22) were recruited. Patients had regular visits with AEs documented and computed tomography (CT) scans every 3 months. CT at screening, at time of GI AE, and at most recent follow-up were reviewed and scored. Endoscopic examination was performed in 5 patients.ResultsOf 22 patients in this cohort, the majority had somatic RET alterations (n = 18), most commonly p.Met918Thr (n = 14). Ten patients (50%) developed GI AEs. Dose reduction was required in 8 of the 10 patients, but none discontinued therapy. The majority had stable disease (n = 17). Gastric and small-bowel edema was evident in symptomatic patients after a median time of 67 weeks' treatment. Histological correlation in 5 patients revealed mucosal edema correlating with radiological evidence of congestion and edema.ConclusionGI AEs with selpercatinib may be more common than previously described. Most are self-limiting but often require dose adjustments. Histological evidence of mucosal edema observed in conjunction with the radiological findings of congestion and wall thickening suggest bowel-wall edema is a predominant mechanism of abdominal pain in these patients.
Project description:Precision oncology has opened a new era in cancer treatment focused on targeting specific cellular pathways directly involved in tumorigenesis. The REarrangement during Transfection (RET) proto-oncogene is involved in the pathogenesis of various thyroid cancer subtypes. Mutations in RET give rise to both hereditary and sporadic medullary thyroid cancer (MTC). RET fusions are found in follicular cell-derived thyroid cancers (papillary, poorly differentiated, and anaplastic). Hence, drugs that block the RET tyrosine kinase receptor have been explored in the management of locally advanced or metastatic thyroid cancer. The multikinase inhibitors (MKIs) with nonselective RET inhibition are sorafenib, lenvatinib, vandetanib, cabozantinib, and sunitinib. Although the efficacy of these drugs varies, a major issue is the lack of specificity resulting in a higher rate of drug-related toxicities, leading to dose reduction, interruption, or discontinuation. Moreover, MKIs are subject to drug resistance by RET Val804 residue gatekeeper mutations. In phase I/II clinical studies, the highly selective first-generation RET inhibitors, selpercatinib and pralsetinib, demonstrate high efficacy in controlling disease even in the presence of gatekeeper mutations combined with greater tolerability. However, resistance mechanisms such as RET solvent front mutations (SFMs) have evolved in some patients, giving the need to develop the selective second-generation RET inhibitors. Although the approval of selpercatinib and pralsetinib in 2020 has profoundly benefited patients with RET-altered thyroid cancer, further research into optimal treatment strategies, mechanisms of drug resistance, long-term consequences of potent RET-inhibition, and development of more effective agents against emergent mutations are much needed.
Project description:BackgroundSelpercatinib, a highly selective and potent REarranged during Transfection (RET) kinase inhibitor, is effective in advanced RET-altered thyroid cancer (TC). However, the efficacy and safety in Chinese patients are unknown.Patients and methodsIn the open-label, multi-center phase II LIBRETTO-321 (NCT04280081) study, Chinese patients with advanced solid tumors harboring RET alterations received selpercatinib 160 mg twice daily. The primary endpoint was objective response rate (ORR; RECIST v1.1) by independent review committee (IRC). Secondary endpoints included duration of response (DoR) and safety. Efficacy was assessed in the primary analysis set [PAS; treated patients with RET fusion-positive TC or RET-mutant medullary TC (MTC) confirmed by central laboratory] and all enrolled patients with MTC.ResultsOf 77 enrolled patients, 29 had RET-mutant MTC and one had RET fusion-positive TC. In the PAS (n = 26), the ORR by IRC was 57.7% [95% confidence interval (CI), 36.9-76.6]. Median DoR was not reached and 93.3% of responses were ongoing at a median follow-up of 8.7 months. In all enrolled MTC patients (n = 29), the ORR by IRC was 58.6% (95% CI, 38.9-76.5). One RET fusion-positive TC patient treated for 23.4 weeks achieved a partial response at week 8 that was ongoing at cutoff. In the safety population (n = 77), 59.7% experienced grade ⩾3 treatment-emergent adverse events (TEAEs). TEAEs led to dose reductions in 32.5% (n = 25) and discontinuations in 5.2% [n = 4; 3.9% (n = 3) considered treatment related] of patients.ConclusionsSelpercatinib showed robust antitumor activity and was well tolerated in Chinese patients with advanced RET-altered TC, consistent with global data from LIBRETTO-001 (NCT04280081).Clinicaltrialsgov identifierNCT04280081 (first posted Feb 21, 2020).
Project description:Rearranged during transfection (RET) is a protooncogene that encodes for receptor tyrosine kinase with downstream effects on multiple cellular pathways. Activating RET alterations can occur and lead to uncontrolled cellular proliferation as a hallmark of cancer development. Oncogenic RET fusions are present in nearly 2% of patients with non-small cell lung cancer (NSCLC), 10-20% of patients with thyroid cancer, and <1% across the pan-cancer spectrum. In addition, RET mutations are drivers in 60% of sporadic medullary thyroid cancers and 99% of hereditary thyroid cancers. The discovery, rapid clinical translation, and trials leading to FDA approvals of selective RET inhibitors, selpercatinib and pralsetinib, have revolutionized the field of RET precision therapy. In this article, we review the current status on the use of the selective RET inhibitor, selpercatinib, in RET fusion-positive tumors: NSCLC, thyroid cancers, and the more recent tissue-agnostic activity leading to FDA approval.
Project description:The efficacy of the highly selective RET inhibitor selpercatinib is now established in RET-driven cancers, and we sought to characterize the molecular determinants of response and resistance. We find that the pre-treatment genomic landscape does not shape the variability of treatment response except for rare instances of RAS-mediated primary resistance. By contrast, acquired selpercatinib resistance is driven by MAPK pathway reactivation by one of two distinct routes. In some patients, on- and off-target pathway reactivation via secondary RET solvent front mutations or MET amplifications are evident. In other patients, rare RET-wildtype tumor cell populations driven by an alternative mitogenic driver are selected for by treatment. Multiple distinct mechanisms are often observed in the same patient, suggesting polyclonal resistance may be common. Consequently, sequential RET-directed therapy may require combination treatment with inhibitors targeting alternative MAPK effectors, emphasizing the need for prospective characterization of selpercatinib-treated tumors at the time of monotherapy progression.
Project description:Selpercatinib (RETEVMO™) is a receptor tyrosine kinase RET (rearranged during transfection) inhibitor being developed by Loxo Oncology for the treatment of cancers harbouring RET alterations. Based on results from the phase I/II LIBRETTO-001 trial, selpercatinib was recently approved by the US FDA for the treatment of RET fusion-positive non-small-cell lung cancer, RET fusion-positive thyroid cancer and RET-mutant medullary thyroid cancer. This article summarizes the milestones in the development of selpercatinib leading to this first approval.
Project description:Rearranged during transfection (RET) is involved in the physiological development of some organ systems. Activating RET alterations via either gene fusions or point mutations are potent oncogenic drivers in non-small cell lung cancer, thyroid cancer, and in multiple diverse cancers. RET-altered cancers were initially treated with multikinase inhibitors (MKIs). The efficacy of MKIs was modest at the expense of notable toxicities from their off-target activity. Recently, highly potent and RET-specific inhibitors selpercatinib and pralsetinib were successfully translated to the clinic and FDA approved. We summarize the current state-of-the-art therapeutics with preclinical and clinical insights of these novel RET inhibitors, acquired resistance mechanisms, and future outlooks.
Project description:BackgroundAlterations involving the RET kinase are implicated in the pathogenesis of lung, thyroid and other cancers. However, the clinical activity of multikinase inhibitors (MKIs) with anti-RET activity in RET-altered patients appears limited, calling into question the therapeutic potential of targeting RET. LOXO-292 is a selective RET inhibitor designed to inhibit diverse RET fusions, activating mutations and acquired resistance mutations.Patients and methodsPotent anti-RET activity, high selectivity, and central nervous system coverage were confirmed preclinically using a variety of in vitro and in vivo RET-dependent tumor models. Due to clinical urgency, two patients with RET-altered, MKI-resistant cancers were treated with LOXO-292, utilizing rapid dose-titration guided by real-time pharmacokinetic assessments to achieve meaningful clinical exposures safely and rapidly.ResultsLOXO-292 demonstrated potent and selective anti-RET activity preclinically against human cancer cell lines harboring endogenous RET gene alterations; cells engineered to express a KIF5B-RET fusion protein -/+ the RET V804M gatekeeper resistance mutation or the common RET activating mutation M918T; and RET-altered human cancer cell line and patient-derived xenografts, including a patient-derived RET fusion-positive xenograft injected orthotopically into the brain. A patient with RET M918T-mutant medullary thyroid cancer metastatic to the liver and an acquired RET V804M gatekeeper resistance mutation, previously treated with six MKI regimens, experienced rapid reductions in tumor calcitonin, CEA and cell-free DNA, resolution of painful hepatomegaly and tumor-related diarrhea and a confirmed tumor response. A second patient with KIF5B-RET fusion-positive lung cancer, acquired resistance to alectinib and symptomatic brain metastases experienced a dramatic response in the brain, and her symptoms resolved.ConclusionsThese results provide proof-of-concept of the clinical actionability of RET alterations, and identify selective RET inhibition by LOXO-292 as a promising treatment in heavily pretreated, multikinase inhibitor-experienced patients with diverse RET-altered tumors.
Project description:Genetic alternation of REarranged during Transfection (RET) that leads to constitutive RET activation is a crucial etiological factor for thyroid cancer. RET is known to regulate mitochondrial processes, although the underlying molecular mechanisms remain unclear. We previously showed that the multi-kinase inhibitors vandetanib and cabozantinib increase the mitochondrial membrane potential (Δψm) in RET-mutated thyroid tumor cells and that this effect can be exploited to increase mitochondrial enrichment of Δψm-sensitive agents in the tumor cells. In this study, we hypothesized that the RET-selective inhibitor, selpercatinib, can increase Δψm and, subsequently, tumor cell uptake of the mitochondria-targeted ubiquinone (MitoQ) to the level to break the mitochondrial homeostasis and induce lethal responses in RET-mutated thyroid tumor cells. We show that selpercatinib significantly increased Δψm, and its combination with MitoQ synergistically suppressed RET-mutated human thyroid tumor cells, which we validated using RET-targeted genetic approaches. Selpercatinib and MitoQ, in combination, also suppressed CCDC6-RET fusion cell line xenografts in mice and prolonged animal survival more effectively than single treatments of each agent. Moreover, we treated two patients with CCDC6-RET or RETM918T thyroid cancer, who could not take selpercatinib at regular doses due to adverse effects, with a dose-reduced selpercatinib and MitoQ combination. In response to this combination therapy, both patients showed tumor reduction. The quality of life of one patient significantly improved over a year until the tumor relapsed. This combination of selpercatinib with MitoQ may have therapeutic potential for patients with RET-mutated tumors and intolerant to regular selpercatinib doses.