LIBRETTO 431
Trial Design
LIBRETTO-431: A Phase III superiority trial of Retevmo versus chemotherapy with or without pembrolizumab for patients with RET fusion-positive advanced or metastatic NSCLC6-8
Efficacy presentation focuses on the cohort of patients that investigators intended to treat with pembrolizumab (ITT-pembro), which included 129 patients who were randomized to Retevmo and 83 patients who were randomized to pembrolizumab plus chemotherapy.
Retevmo was dosed at 160 mg BID. Pembrolizumab was dosed at 200 mg Q3W. Chemotherapy included pemetrexed (500 mg/m2 Q3W) and carboplatin (AUC 5 Q3W) or cisplatin (75 mg/m2 Q3W).
Patients were stratified per investigator's choice of treatment with or without pembrolizumab if randomized to the control arm. Choice was declared prior to randomization. The subset of patients randomized with the intent not to receive pembrolizumab was less than 20% of total randomized patients, and is analyzed only as part of the intent-to-treat population.
Additional stratification factors: geography, brain metastases at baseline per investigator assessment.
PFS
In patients with advanced or metastatic RET fusion-positive NSCLC
Retevmo demonstrated superior PFS compared to pembrolizumab plus chemotherapy7,9
Median PFS: 24.8 months (95% CI: 17.3, NE) with Retevmo (n=159) vs 11.2 months (95% CI: 8.8, 16.8) for the entire control arm (n=102).7,9,§
PFS was assessed in all randomized patients.
Based on an interim analysis with a data cutoff date of May 1, 2023.7,9
Select Important Safety Information
Hepatotoxicity: Serious hepatic adverse reactions occurred in 3% of patients treated with Retevmo. Increased aspartate aminotransferase (AST) occurred in 59% of patients, including Grade 3 or 4 events in 11% and increased alanine aminotransferase (ALT) occurred in 55% of patients, including Grade 3 or 4 events in 12%. Monitor ALT and AST prior to initiating Retevmo, every 2 weeks during the first 3 months, then monthly thereafter and as clinically indicated. Withhold, reduce dose, or permanently discontinue Retevmo based on the severity.
ORR and DoR
Objective response rate and duration of response for Retevmo vs pembrolizumab plus chemotherapy7,9
ORR:
84% (95% CI: 77, 89; 7.5% CR + 76% PR) with Retevmo (n=159) vs 63% (95% CI: 53, 72; 4.9% CR + 58% PR) for the entire control arm (n=102)
Median DoR:
24.2 months (95% CI: 17.9, NE) Retevmo (n=159) vs 12.0 months (95% CI: 9.7, 23.3) for the entire control arm (n=102)*
ORR, a secondary endpoint, was defined as CR+PR and was assessed by the IRC according to RECIST v1.1.9 Based on an interim analysis with a data cutoff date of May 1, 2023.7,9
431 CNS ORR and DoR
Retevmo had CNS activity¶ in patients with RET fusion-positive advanced or metastatic NSCLC7,9
Responses in patients with measurable CNS metastases at baseline
CNS Efficacy Data for Retevmo vs ITT
CNS ORR: 84% (95% CI: 60, 97; 32% CR + 53% PR) with Retevmo (n=16/19) vs 58% (95% CI: 28, 85; 17% CR + 42% PR) in the ITT (n=7/12)7,9
CNS Median DoR: NE months (95% CI: 7.4, NE) Retevmo vs 13.4 months (95% CI: 3.5, NE) in the ITT7,9,**
CNS ORR (defined as CR+PR) and CNS DoR were prespecified secondary endpoints in the LIBRETTO-431 trial and were evaluated and assessed by IRC according to RECIST v1.1.7,9
Based on an interim analysis with a data cutoff date of May 1, 2023.7,9
Select Important Safety Information
Severe, life-threatening, and fatal interstitial lung disease (ILD)/pneumonitis can occur in patients treated with Retevmo. ILD/pneumonitis occurred in 1.8% of patients who received Retevmo, including 0.3% with Grade 3 or 4 events, and 0.3% with fatal reactions. Monitor for pulmonary symptoms indicative of ILD/pneumonitis. Withhold Retevmo and promptly investigate for ILD in any patient who presents with acute or worsening of respiratory symptoms which may be indicative of ILD (e.g., dyspnea, cough, and fever). Withhold, reduce dose, or permanently discontinue Retevmo based on severity of confirmed ILD.
431 Risk of CNS Progression
Risk of CNS as the first site of progression was reduced with Retevmo compared to pembrolizumab plus chemotherapy7,9
12-Month CIR for Patients with or without Baseline CNS Metastases (N=192)7,9
12-Month CIR (cumulative incidence rate) for Retevmo vs ITT7,9
With or without Baseline CNS Metastases: 5.2% (95% CI: 2.3, 9.9) with Retevmo (n=146) vs 19.4% (95% CI: 11.4, 29.1) in the ITT (n=88) [HR=0.26; 95% CI: 0.11, 0.59]
With Baseline CNS Metastases: 25.5% (95% CI: 10.0, 44.4) with Retevmo (n=25) vs 35.7% (95% CI: 17.4, 54.5) in the ITT (n=26) [HR=0.52; 95% CI: 0.19, 1.47]
Without Baseline CNS Metastases: 0.9% (95% CI: 0.1, 4.3) with Retevmo (n=121) vs 12.2% (95% CI: 4.8, 23.4) in the ITT (n=62) [HR=0.16; 95% CI: 0.04, 0.66]
Safety
Safety and tolerability were evaluated in LIBRETTO-4317,10
Select Adverse Events (≥20%) in Patients Who Received Retevmo in LIBRETTO-4317,10
aDiarrhea includes diarrhea, anal incontinence
bDry mouth includes dry mouth, mucosal dryness
cAbdominal pain includes abdominal pain upper, abdominal pain, abdominal discomfort, abdominal pain lower, gastrointestinal pain
dEdema includes peripheral edema, face edema, edema, periorbital edema, swelling face, peripheral swelling, penile edema, scrotal edema, eye edema, eyelid edema, localized edema, orbital edema, orbital swelling, periorbital swelling
eFatigue includes fatigue, asthenia, malaise
fRash includes rash, dermatitis, rash maculo-papular, skin exfoliation, dermatitis allergic, rash macular, rash papular, rash pustular, rash erythematous, rash vesicular, urticaria
Select Laboratory Abnormalities (≥20%) Worsening from Baseline in Patients Who Received Retevmo in LIBRETTO-4317,10,a
- Based on an interim analysis with a data cutoff date of May 1, 2023.7,10
- 10.1% (n=16) of patients permanently discontinued Retevmo (N=158) due to adverse events. 7.1% (n=11) were considered treatment-related, as assessed by trial investigator. Adverse events resulting in permanent discontinuation in ≥ 2 patients included increased ALT (n=2) and myocardial infarction (n=2)
- Serious adverse events occurred in 34.8% of patients who received Retevmo. The most frequently reported serious adverse events (in ≥2% of patients) were pleural effusion, hepatic function abnormal, ascites, cholecystitis, and pneumonia.
- More deaths were observed among those receiving Retevmo versus the entire control arm while on treatment or within 30 days of the last dose (n=7/158 vs n=0/98).
- More deaths were observed among those receiving Retevmo versus the entire control arm while on treatment or within 30 days of the last dose (n=7/158 vs n=0/98). Fatal adverse events occurred in 4.4% of patients; fatal adverse events included myocardial infarction (n=2), acute respiratory failure (n=1), cardiac arrest (n=1), malnutrition (n=1), respiratory failure (n=1), and sudden death (n=1). The deaths in 2 of 7 patients were judged by the investigators to be related to Retevmo (malnutrition and sudden death). One additional patient randomized to the control arm had a fatal event (respiratory failure) during crossover treatment with Retevmo.
- Dose interruptions and dose reductions due to adverse events occurred in 75.9% and 51.3% of patients who received Retevmo, respectively. See full Prescribing Information for dose modifications.
- Adverse events requiring dosage interruption in ≥5% of patients included increased ALT, increased AST, COVID-19, diarrhea, QT prolongation, and hypertension.
- Adverse events requiring dosage reductions in ≥2% of patients included increased ALT, increased AST, QT prolongation, hypertension, hepatic function abnormal, and platelet count decreased.
- Clinically relevant toxicities included decreased appetite (17.1%), hemorrhage (16.5%), interstitial lung disease/pneumonitis (4.4%), hypothyroidism (3.2%), hypersensitivity (2.5%), chylothorax (< 1%)
- Five randomized patients never received study drug and were excluded from the safety analysis.
- Graded according to National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) version 5.0.
Summary
In the 1L treatment of advanced or metastatic RET-fusion positive NSCLC
Retevmo is the first and only targeted agent to have demonstrated superior PFS in a Phase III head-to-head trial against pembrolizumab plus chemotherapy7,9
- LIBRETTO-431 (N=261) is a randomized, global, multicenter, open-label, Phase III trial that evaluated Retevmo versus chemotherapy with or without pembrolizumab in treatment-naive adult patients with advanced or metastatic RET fusion-positive NSCLC, including those with brain metastases.
- The primary endpoint was PFS for Retevmo against chemotherapy with pembrolizumab and against the entire control arm.
- 10% of patients permanently discontinued treatment due to AEs with Retevmo (n=16/158)10
Retevmo may affect both healthy cells and tumor cells, which can result in side effects, some of which can be serious.1
Based on an interim analysis with a data cutoff date of May 1, 2023.7,9
Efficacy outcomes for patients treated with Retevmo (n=159) versus the entire control arm (n=102):
- Median PFS = 24.8 months (95% CI: 17.3, NE) vs 11.2 months (95% CI: 8.8, 16.8)
- ORR = 84% (95% CI: 77, 89) vs 63% (95% CI: 53, 72)
- Median DoR = 24.2 months (95% CI: 17.9, NE) vs 12.0 months (95% CI: 9.7, 23.3)
NSCLC Summary
For patients with locally advanced or metastatic NSCLC
Retevmo was granted approval based on LIBRETTO-001, a Phase I/II trial
LIBRETTO-001 Trial Design
The phase I/II, multicohort, open-label, single-arm, multicenter LIBRETTO-001 trial enrolled a pooled safety population of 796 patients, including patients with locally advanced or metastatic RET fusion-positive NSCLC.* Major efficacy outcomes were ORR and DoR. Other efficacy outcomes, evaluated in subsets of patients, included CNS ORR, CNS DoR, PFS, OS, time to response, and best change in tumor size from baseline. In phase II, the dose for Retevmo was 160 mg PO BID.1-4
The pooled safety population also included patients with advanced or metastatic RET fusion-positive thyroid cancer (non-MTC),† patients with advanced or metastatic RET-mutant MTC, patients with RET fusion-positive solid tumors (other than NSCLC or thyroid),‡ and patients with other cancers, including cancers without a RET alteration.3
*Patients with locally advanced or metastatic RET fusion-positive NSCLC who had progressed on platinum-based chemotherapy and those without prior systemic therapy were enrolled in separate cohorts.1
†Non-MTC by histology included papillary (n=54), poorly differentiated (n=6), anaplastic (n=4), and Hurthle cell (n=1).1
‡Other RET fusion-positive solid tumors included pancreatic cancer (n=11), colon cancer (n=10), and salivary cancer (n=4).1
BID=twice daily; CNS=central nervous system; DoR=duration of response; NSCLC=non-small cell lung cancer; ORR=objective response rate; OS=overall survival; PFS=progression-free survival; PO=orally; RET=rearranged during transfection.
- Time-to-event endpoints are not interpretable in a single-arm study. The clinical significance of this descriptive analysis is not known.
- ORR was defined as CR + PR and was assessed by IRC according to RECIST v1.1.1
- ORR, DoR, CNS ORR, CNS DoR results reviewed by an IRC.1,5
- CNS ORR was a prespecified secondary endpoint that was evaluated and confirmed by an IRC.1
Select Important Safety Information
Hypertension occurred in 41% of patients, including Grade 3 hypertension in 20% and Grade 4 in one (0.1%) patient. Overall, 6.3% had their dose interrupted and 1.3% had their dose reduced for hypertension. Treatment-emergent hypertension was most commonly managed with anti-hypertension medications. Do not initiate Retevmo in patients with uncontrolled hypertension. Optimize blood pressure prior to initiating Retevmo. Monitor blood pressure after 1 week, at least monthly thereafter, and as clinically indicated. Initiate or adjust anti-hypertensive therapy as appropriate. Withhold, reduce dose, or permanently discontinue Retevmo based on the severity.
INDICATIONS
Retevmo is a kinase inhibitor indicated for the treatment of:
- adult patients with locally advanced or metastatic non-small cell lung cancer (NSCLC) with a rearranged during transfection (RET) gene fusion, as detected by an FDA-approved test
- adult and pediatric patients 2 years of age and older with advanced or metastatic medullary thyroid cancer (MTC) with a RET mutation, as detected by an FDA-approved test, who require systemic therapy*
- adult and pediatric patients 2 years of age and older with advanced or metastatic thyroid cancer with a RET gene fusion, as detected by an FDA-approved test, who require systemic therapy and who are radioactive iodine-refractory (if radioactive iodine is appropriate)
- adult and pediatric patients 2 years of age and older with locally advanced or metastatic solid tumors with a RET gene fusion, as detected by an FDA-approved test, that have progressed on or following prior systemic treatment or who have no satisfactory alternative treatment options*
*These indications are approved under accelerated approval based on overall response rate (ORR) and duration of response (DoR). Continued approval for these indications may be contingent upon verification and description of clinical benefit in confirmatory trials.