Pralsetinib Clinical Guide: Discontinuation Principles, Drug Comparisons, and Treatment Strategies

　　1.Discontinuation Principles and Long-Term Management

　　Pralsetinib is not a medication that"once started,can never be stopped,"but any discontinuation decision must be grounded in clear clinical justification rather than patient self-determination.

　　Standard Treatment Principle:Pralsetinib should be taken continuously as long as the disease has not progressed and toxicity remains tolerable.The fundamental concept of targeted therapy is to maintain tumor control through sustained inhibition of the driver gene.Discontinuing treatment without evidence of disease progression may lead to rapid tumor rebound and clinical deterioration.

　　Temporary Interruption or Dose Reduction for Adverse Events:When patients experience intolerable adverse reactions—such as uncontrolled hypertension,interstitial lung disease,or severe hepatic dysfunction—treatment may be temporarily suspended.Once the adverse event resolves to Grade 1 or returns to baseline,therapy can be restarted at a reduced dose.If the reduced dose remains intolerable,permanent discontinuation should be considered.

　　Exploring Discontinuation After Deep Remission:In cases where patients achieve sustained deep remission(e.g.,complete response maintained for over 12 months),discontinuation with close observation may be explored within specific clinical trial settings.However,this does not currently represent standard clinical practice.All discontinuation or dose modification decisions must be made under the comprehensive evaluation and close supervision of the treating physician,accompanied by regular imaging and laboratory surveillance.

　　2.Pralsetinib vs.Selpercatinib:Selective RET Inhibitor Comparison

　　The two globally approved highly selective RET inhibitors are pralsetinib and selpercatinib.Both have demonstrated exceptional efficacy in RET fusion-positive non-small cell lung cancer(NSCLC)and thyroid cancer,though they differ in certain nuances.

　　Efficacy Comparison:In treatment-naïve RET fusion-positive NSCLC,pralsetinib achieves an objective response rate(ORR)of approximately 70%–80%,while selpercatinib reports comparable figures above 70%.Both agents demonstrate strong intracranial activity against brain metastases.Notably,a 2024 real-world study from the Mayo Clinic revealed that under similar baseline conditions,the pralsetinib group achieved a 2-year progression-free survival(PFS)rate of 73.6%,with a longer intracranial duration of response(median 14.8 months vs.9.5 months for selpercatinib),providing valuable real-world evidence to inform clinical selection.

　　Safety Profiles:Pralsetinib has a relatively focused adverse event spectrum,with slightly higher rates of hypertension,constipation,and elevated liver enzymes,but its toxicity profile is narrow,with events typically early-onset and reversible.Selpercatinib is more commonly associated with diarrhea and hypertension,and some patients may experience QT interval prolongation.Both agents have manageable adverse event profiles,though the monitoring focus and management rhythm differ.

　　Selection Strategy:No head-to-head randomized Phase III trial has directly established superiority of one agent over the other.Clinical selection should comprehensively consider individual tolerability,comorbidities,drug accessibility,and health insurance coverage to achieve personalized treatment.

　　3.First-Line Strategy:Pralsetinib Monotherapy Standard

　　For treatment-naïve patients with RET fusion-positive metastatic NSCLC or advanced RET fusion-positive thyroid cancer,pralsetinib monotherapy is the recognized first-line standard of care.

　　Dosing Regimen:The recommended dose is 400 mg taken orally once daily on an empty stomach(no food for at least 2 hours before and 1 hour after dosing)to ensure optimal absorption and bioavailability.

　　Clinical Benefits:First-line monotherapy achieves an ORR exceeding 70%in treatment-naïve patients,with a median PFS surpassing 20 months.Latest long-term follow-up data indicate that median overall survival in RET fusion-positive NSCLC patients can exceed 50 months,underscoring the substantial survival benefit of early targeted intervention.

　　Regimen Advantages:This approach offers convenient once-daily oral dosing without the need for combination chemotherapy or immunotherapy,making it suitable for most patients with good performance status.For patients with relatively localized disease and mild symptoms,monotherapy alone can achieve deep and durable disease control,significantly enhancing quality of life.

　　4.Later-Line Strategy:Clinical Benefits and Dose Management in Pretreated Patients

　　For patients with RET fusion-positive solid tumors who have progressed after prior platinum-based chemotherapy,immunotherapy,or other systemic treatments,pralsetinib as a later-line therapy continues to deliver meaningful clinical benefits.

　　Efficacy Outcomes:In pretreated patients,pralsetinib achieves an ORR of approximately 50%–60%,with a median duration of response of about 15 months.Although these figures are lower than first-line results,they remain clinically significant for patients who have already undergone multiple prior lines of therapy.

　　Dosing and Monitoring:The standard dose and administration in the later-line setting are identical to first-line treatment(400 mg once daily,fasting).However,because prior treatments may have compromised bone marrow reserve or hepatic/renal function,closer monitoring of blood counts and organ function is required during therapy.For patients with baseline hepatic or renal impairment,initiating treatment at a lower dose(e.g.,300 mg daily)with gradual escalation to the standard dose upon confirmed tolerability may be considered.

　　Special Considerations for Brain Metastases:In second-line and beyond settings,patients with concurrent brain metastases do not require dose adjustments specifically for intracranial disease.Pralsetinib possesses excellent blood-brain barrier penetration,enabling effective control of intracranial lesions and providing a critical treatment option for this challenging patient population.