Speck, Rebecca M.

1001 Background: Imlunestrant (imlu) is a next-generation, brain-penetrant, oral selective estrogen receptor degrader. The EMBER-3 trial, in patients (pts) with ER+, HER2- ABC who had disease progression on or after aromatase inhibitor-based therapy, showed significant progression free survival (PFS) improvement with imlu vs standard therapy (SOC, fulvestrant or exemestane) in pts with ESR1 mutations ( ESR1 m), and with imlunestrant+abemaciclib (imlu+abema) vs imlu in all pts, regardless of ESR1 m. Exploratory PRO analyses are presented here. Methods: EORTC QLQ-C30 was administered at baseline (BL) and every 8 weeks until treatment discontinuation. Prespecified QLQ-C30 analysis used a longitudinal mixed model for repeated measures to calculate mean change from BL in pts with BL and ≥1 post-BL score. PRO-CTCAE (diarrhea frequency) was administered weekly, reporting 0 (never) to 4 (almost constantly). PRO-CTCAE (injection site reaction [ISR]) was administered to fulvestrant recipients weekly for 2 weeks post-injection, reporting yes/no (pain, swelling, redness). Descriptive analysis was used for PRO-CTCAE. Results: In pts with ESR1 m, imlu monotherapy was associated with many improved or maintained EORTC QLQ-C30 scores, whereas scores with SOC were declined or maintained. Specifically, pts with ESR1 m on imlu had improved global health status (GHS)/quality of life (QOL) and physical function (PF) scores, while scores with SOC declined (mean change differences between treatments: 9.9 [0.1, 19.7] and 6.2 [-0.8, 13.1], respectively). These PRO findings mirror the PFS findings in this group. In the overall population, GHS/QOL scores declined similarly with imlu vs SOC (mean change differences: 0.5 [-4.7, 5.7]), while PF scores were maintained with imlu vs a slight decline with SOC (mean change difference: 2.5 [-1.1, 6.1]). Most fulvestrant recipients (72%) reported ISR at any time while on treatment, with a mean of 31% during the first week of the first 6 cycles. Imlu+abema vs imlu showed broadly similar declines in all pts, with minimal mean change differences in GHS/QOL and PF scores (0.8 [-7.4, 5.9]; -2.2 [-6.6, 2.2], respectively). Pts reported similarly low rates of “frequent” or “almost constant” diarrhea with imlu (3%) and SOC (2%) and higher rates with imlu+abema (22%). Conclusions: PROs from EMBER-3 demonstrated that patients with ESR1 m had better GHS/QOL and PF with imlu vs SOC, mirroring efficacy results. While the frequency of CTCAE defined ISRs was low, the high rate of PRO-CTCAE ISR demonstrates that this clinically relevant adverse event is underappreciated by physicians. Additionally, all pts had generally comparable GHS/QOL and PF with imlu+abema vs imlu. Overall, these results support the efficacy and safety of imlu compared to existing SOC. Clinical trial information: NCT04975308 .

AbstractBackgroundThe purpose of this study was to evaluate the measurement properties of the American Neurogastroenterology and Motility Society Gastroparesis Cardinal Symptom Index‐Daily Diary, a patient‐reported outcome instrument developed to meet US FDA recommendations for a symptom‐based clinical trial endpoint in gastroparesis. The ANMS GCSI‐DD assesses nausea, early satiety, postprandial fullness, and upper abdominal pain on a severity score from none (0) to very severe (4) and number of vomiting episodes during the past 24 hours. The composite score includes the first four symptoms, the core symptom score includes all five symptoms.MethodsSeventy‐one patients diagnosed with idiopathic or diabetic gastroparesis were recruited for a four‐week observational study. Patients completed the ANMS GCSI‐DD at home between Baseline and Week 4. Statistical analyses included confirmatory factor analysis, item response theory analysis, internal consistency, test‐retest reliability, and construct and known‐groups validity.Key ResultsUnidimensionality for the composite and core symptom scores was supported, and items exhibited good fit. Internal consistency (Cronbach's alpha =0.85 and 0.83) and test‐retest reliability were 0.89 and 0.88, for composite and core symptom scores, respectively. Convergent validity was supported by strong correlations with patient‐reported and clinician measures. Baseline and Week 4 scores differed for three measures used to define disease severity status (P < 0.0001), supporting known‐groups validity.Conclusions & InferencesThe ANMS GCSI‐DD has excellent reliability and validity, supporting its use to assess symptom‐based endpoints in gastroparesis clinical studies. Further analyses will be conducted using clinical trial data to ascertain treatment responsiveness and define a responder.