BACKGROUND: Pralsetinib, a selective RET targeted tyrosine kinase inhibitor (TKI), has been approved for treating locally advanced or metastatic RET fusion-positive NSCLC in adults who have previously received platinum-based chemotherapy in China.
METHODS: In this retrospective analysis conducted at Hunan Cancer Hospital in China, we examined 36 patients with advanced NSCLC with RET fusion, who were treated with pralsetinib between January 2021 and December 2023. The study focused on assessing the efficacy (Progression-free survival (PFS) and overall survival (OS)) and safety profile of pralsetinib in these patients. Statistical analyses were conducted using SPSS version 20.0, with a significance level set at p < 0.05.
RESULTS: The results revealed that pralsetinib exhibited significant activity in this patient cohort. Kaplan-Meier survival analysis indicated a median PFS of 10.7 months and a median OS of 21.2 months. The overall response rate(ORR) and disease control rate (DCR) was 55.6 % and 72.2 %, respectively. Pralsetinib was generally well tolerated, with most adverse events being mild to moderate (grades 1-2). The most common serious adverse events (≥grade 3) observed were lymphopenia (13.9 %), hypertension (11.1 %), leukopenia (8.3 %), neutropenia (8.3 %), and creatine kinase elevation (8.3 %).
CONCLUSIONS: Pralsetinib demonstrated promising activity in patients with advanced NSCLC harboring RET fusion with a favorable safety profile.

UNASSIGNED: Pralsetinib, a targeted inhibitor of the RET enzyme, plays a critical role in the treatment of adult patients with locally advanced or metastatic non-small cell lung cancer (NSCLC) characterized by RET gene fusion mutations following platinum-based chemotherapy. Nevertheless, impurities resulting from the manufacturing and degradation of pralsetinib have the potential to impact its therapeutic effectiveness and safety profile.
UNASSIGNED: To address this issue, a liquid chromatography method was developed and validated for the specific identification of pralsetinib and its related impurities. The separation of pralsetinib and its related impurities was achieved via a Waters X Bridge C18 column with dimensions of 4.6 mm × 250 mm and a particle size of 5 μm. Mobile phase A was composed of 20 mmol/L potassium dihydrogen phosphate (KH2PO4) and acetonitrile (ACN) at a volume ratio of 19:1, while mobile phase B consisted solely of ACN, utilizing a gradient elution technique. Detection was performed at a wavelength of 260 nm, with an injection volume of 10 μL and a flow rate of 1.0 mL/min.
UNASSIGNED: The chromatographic method established in this study was validated according to the ICH Q2 (R1) guidelines. The method demonstrated excellent linearity over a specific concentration range (imp-A: 0.035-10.21 μg/mL; imp-B: 0.09-10.16 μg/mL; imp-C: 0.15-10.19 μg/mL; pralsetinib: 0.04-10.32 μg/mL). Additionally, the method possesses high sensitivity, with detection limits for impurities A, B, C, and pralsetinib of 0.01, 0.03, 0.015, and 0.013 μg/mL, respectively, and quantification limits of 0.035, 0.09, 0.05, and 0.04 μg/mL, respectively. In terms of specificity, stability, repeatability, accuracy, and robustness, the method met the validation acceptance criteria. Overall, the chromatographic technique established in this study can effectively separate pralsetinib and its impurities, providing reliable assurance for the accurate detection and quantification of impurities.
UNASSIGNED: The chromatographic method developed in this study can be utilized for the detection of pralsetinib and its impurities, offering a crucial reference for research on the quality of pralsetinib.

RET fusions are relatively rare in Non-Small-Cell Lung Cancers (NSCLCs), being around 1-2% of all NSCLCs. They share the same clinical features as the other fusion-driven NSCLC patients, as follows: younger age, adenocarcinoma histology, low exposure to tobacco, and high risk of spreading to the brain. Chemotherapy and immunotherapy have a low impact on the prognosis of these patients. Multitargeted RET inhibitors have shown modest activity jeopardized by high toxicity. New potent and selective RET inhibitors (RET-Is) (pralsetinib and selpercatinib) have achieved a higher efficacy minimizing the known toxicities of the multitargeted agents. This review will describe the sensitivity of immune-checkpoint inhibitors (ICIs) in RET fusion + NSCLC patients, as well their experiences with the \'old\' multi-targeted RET inhibitors. This review will focus on the advent of new potent and selective RET-Is. We will describe their efficacy as well as the main mechanisms of resistance to them. We will further proceed to deal with the new drugs and strategies proposed to overcome the resistance to RET-Is. In the last section, we will also focus on the safety profile of RET-Is, dealing with the main toxicities as well as the rare but severe adverse events.

Selective rearranged during transfection (RET) tyrosine kinase inhibitor, pralsetinib, demonstrated clinical efficacy and was well tolerated in lung and thyroid cancers with RET gene mutations or fusions in clinical trials. While the latter focused on the risk of pneumonitis, there is a lack of data regarding other types of infectious risks associated with pralsetinib. Herein, we report the case of a 53-year-old patient with a CCDC6-RET fusion neuroendocrine tumor, who achieved a partial response with pralsetinib as the fifth-line therapy. Of particular note, during pralsetinib therapy, the clinical course was complicated by five severe infectious events, namely, two oxygen-requiring pneumonias, two distinct spondylodiscitis, and one pneumocystis. Our study highlights the increased risk of any type of opportunistic infectious event with pralsetinib, but not selpercatinib, which is probably caused by off-target JAK1/2 inhibition.

The application of adjuvant treatment has significantly enhanced the survival of patients with resectable non-small cell lung cancer (NSCLC) carrying driver gene mutations. However, adjuvant-targeted therapy remains controversial for some NSCLC patients carrying rare gene mutations such as RET, as there is currently a lack of confirmed randomized controlled trials demonstrating efficacy. In this report, we describe the case of a 58-year-old man with stage IIIA NSCLC who underwent complete lobectomy with selective lymph node dissection. Postoperative next-generation sequencing revealed that the patient harbored a rare KIF13A-RET fusion. The patient elected to receive adjuvant treatment with pralsetinib monotherapy and underwent serial circulating tumor DNA (ctDNA) monitoring after surgery. During follow-up, despite experiencing dose reduction and irregular medication adherence, the patient still achieved a satisfactory disease-free survival (DFS) of 27 months. Furthermore, ctDNA predicted tumor recurrence 4 months earlier than imaging techniques. The addition of bevacizumab to the original regimen upon recurrence continued to be beneficial. Pralsetinib demonstrated promising efficacy as adjuvant therapy, while ctDNA analysis offered a valuable tool for early detection of tumor recurrence. By leveraging targeted therapies and innovative monitoring techniques, we aim to improve outcomes and quality of life for NSCLC patients in the future.

Dynamic in vitro absorption systems and mechanistic absorption modeling via PBPK have both shown promise in predicting human oral absorption, although these efforts have been largely separate; this work aimed to integrate knowledge from these approaches to investigate the oral absorption of a RET inhibitor, pralsetinib, with BCS Class II properties. Tiny-TIM (TIM B.V., Weteringbrug​, The Netherlands) is a dynamic in vitro model with close simulation of the successive physiological conditions of the human stomach and small intestine. Tiny-TIM runs with pralsetinib were performed at doses of 200 mg and 400 mg under fasting conditions. Mechanistic modeling of absorption was performed in Simcyp V21 (Certara, Manchester, UK). Pralsetinib fasted bioaccessibility in the Tiny-TIM system was 63% at 200 mg and 53% at 400 mg; a 16% reduction at 400 mg was observed under elevated gastric pH. Maximum pralsetinib solubility from the small intestinal compartment in Tiny-TIM directly informed the supersaturation/precipitation model parameters. The PBPK model predicted a similar fraction absorbed at 200 mg and 400 mg, consistent with the dose proportional increases in observed pralsetinib exposure. Integrating dynamic in vitro systems with mechanistic absorption modeling provides a promising approach for understanding and predicting human absorption with challenging low solubility compounds.

Selpercatinib, a potent and highly selective RET kinase inhibitor with significant CNS activity, has recently gained US approval for the treatment of NSCLC harboring RET fusions (RET+) based on a large-scale single-arm study. The LIBRETTO-431 trial was the global pivotal registration phase 3 trial comparing selpercatinib to platinum-based chemotherapy with or without pembrolizumab as the first-line treatment of patients with advanced RET+ NSCLC. Never-smokers constituted 67.4% of the RET+ NSCLC patients enrolled. KIF5B-RET made up the vast majority (77%) of the RET+ fusion variant with known fusion partner. The results of this study demonstrated significant improvement in progression-free survival (PFS) benefit as well as impressive intracranial disease response in participants treated with selpercatinib as compared to those treated with chemotherapy, with a HR [hazard ratio] of 0.46 (95% CI 0.33-0.70; P < 0.001) for the intention-to-treat (ITT)-pembrolizumab group and HR of 0.46 (95% CI 0.31-0.70, P < 0.001) for the overall ITT-group of patients. The addition of pembrolizumab to platinum/pemetrexed chemotherapy resulted in numerically identical PFS (11.2 months). These results point to selpercatinib\'s superiority to traditional chemotherapy regimens in the treatment of NSCLC harboring RET fusions and add to literature on the salience of targeted precision oncology and lack of efficacy of immune checkpoint inhibitor in NSCLC patients with never-smoker predominant actionable driver mutations. RET+ NSCLC should be added to the list of molecular subtypes (EGFR+, ALK+, ROS1+) of NSCLC to be excluded in chemoimmunotherapy trial.

Pralsetinib is a kinase inhibitor indicated for the treatment of metastatic rearranged during transfection (RET) fusion-positive non-small cell lung cancer. Pralsetinib is primarily eliminated by the liver and hence hepatic impairment (HI) is likely alter its pharmacokinetics (PK). Mild HI has been shown to have minimal impact on the PK of pralsetinib. This hepatic impairment study aimed to determine the pralsetinib PK, safety and tolerability in subjects with moderate and severe HI, as defined by the Child-Pugh and National Cancer Institute Organ Dysfunction Working Group (NCI-ODWG) classification systems, in comparison to subjects with normal hepatic function. Based on the Child-Pugh classification, subjects with moderate and severe HI had similar systemic exposure (area under the plasma concentration time curve from time 0 to infinity [AUC0-∞]) to pralsetinib, with AUC0-∞ geometric mean ratios (GMR) of 1.12 and 0.858, respectively, compared to subjects with normal hepatic function. Results based on the NCI-ODWG classification criteria were comparable; the AUC0-∞ GMR were 1.22 and 0.858, respectively, for subjects with moderate and severe HI per NCI-ODWG versus those with normal hepatic function. These results suggested that moderate and severe hepatic impairment did not have a meaningful impact on the exposure to pralsetinib, thus not warranting a dose adjustment in this population.

BACKGROUND: Ultra-performance Liquid Chromatography-tandem Mass Spectrometry (UPLC-MS/MS) is widely used for concentration detection of many Tyrosine Kinase Inhibitors (TKIs), including afatinib, crizotinib, and osimertinib. In order to analyze whether pralsetinib takes effect in Rearranged during Transfection (RET)-positive patients with central nervous system metastasis, we aimed to develop a method for the detection of pralsetinib concentrations in human plasma and Cerebrospinal Fluid (CSF) by UPLC-MS/MS.
METHODS: The method was developed using the external standard method, and method validation included precision, accuracy, stability, extraction recovery, and matrix effect. Working solutions were all obtained based on stock solutions of pralsetinib of 1mg/mL. The plasma/CSF samples were precipitated by acetonitrile for protein precipitation and then separated on an ACQUITY UPLC HSS T3 column (2.1×100 mm, 1.8 μm) with a gradient elution using 0.1% formic acid (solution A) and acetonitrile (solution B) as mobile phases at a flow rate of 0.4 mL/min. The tandem mass spectrometry was performed by a triple quadrupole linear ion trap mass spectrometry system (QTRAPTM 6500+) with an electrospray ion (ESI) source and Analyst 1.7.2 data acquisition system. Data were collected in Multiple Reaction Monitoring (MRM) and positive ionization mode.
RESULTS: A good linear relationship of pralsetinib in both plasma and CSF was successfully established, and the calibration ranges were found to be 1.0-64.0 μg/mL and 50.0ng/mL-12.8 μg/mL for pralsetinib in the plasma and CSF, respectively. Validation was performed, including calibration assessment, selectivity, precision, accuracy, matrix effect, extraction recovery, and stability, and all results have been found to be acceptable. The method has been successfully applied to pralsetinib concentration detection in a clinical sample, and the concentrations have been found to be 475 ng/mL and 61.55 μg/mL in the CSF and plasma, respectively.
CONCLUSIONS: We have developed a quick and effective method for concentration detection in both plasma and CSF, and it can be applied for drug monitoring in clinical practice. The method can also provide a reference for further optimization.

Pralsetinib is a highly potent oral kinase inhibitor of oncogenic RET (rearranged during transfection) fusions and mutations. Pralsetinib received approval from the United States Food and Drug Administration for the treatment of patients with metastatic RET fusion-positive non-small cell lung cancer (NSCLC), and received accelerated approval for the treatment of patients with RET fusion-positive thyroid cancer. Exposure-response (ER) analyses of efficacy were performed separately in patients with thyroid cancer and in patients with NSCLC, but data for all patients were pooled for the safety analysis. ER models were developed with time-varying exposure; the effect of covariates was also examined. For patients with NSCLC, a higher starting dose was associated with improved progression-free survival (PFS), but this improvement did not correlate with a higher exposure overall. Significant covariates included sex and baseline Eastern Cooperative Oncology Group (ECOG) score. For patients with thyroid cancer, a higher exposure was associated with improved PFS. Significant covariates included prior systemic cancer therapy and ECOG score. For safety, higher exposure was associated with a greater risk of grade ≥3 anemia, pneumonia, and lymphopenia. Patients with an ECOG score of ≥1 had an increased risk of grade ≥3 pneumonia. Non-White patients had a lower risk of grade ≥3 lymphopenia. ER analysis revealed that higher pralsetinib exposure was associated with improved PFS in thyroid cancer, but not in NSCLC. However, a higher starting dose (ie, 400 vs ≤300 mg daily) was correlated with better PFS for all indications. Higher exposure was also associated with an increased risk of grade ≥3 adverse events (AEs); however, the overall incidence of these events was acceptably low (≤20%). This analysis supports the use of a 400 mg starting dose of pralsetinib, allowing for dose reduction in the event of AEs.