Real-World Treatment Patterns and Outcomes in Patients with Primary Immune Thrombocytopenia Treated with Avatrombopag in the United States: Real-AVA 2.0 Interim Analysis Results

Introduction: Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by low platelet counts (PCs), which may lead to serious bleeding episodes. Thrombopoietin-receptor agonists (TPO-RAs), including avatrombopag (AVA), are approved for the treatment of adults with chronic ITP. Response to AVA is typically defined as the achievement of target PC levels and reductions in the use of concomitant medications such as steroids. In clinical trials, >90% of patients (Pts) achieved a response to AVA at a threshold of PC ≥50k/µL. However, limited real-world evidence exists on AVA use and effectiveness. Additionally, clinical studies had limited follow-up, whereas real-word data provides an opportunity to evaluate long-term effectiveness. The REAL-AVA 2.0 study aims to describe treatment patterns and clinical outcomes among Pts with primary ITP receiving AVA in clinical practice in the US. Methods: Data was collected in an ongoing retrospective, multi-site chart review of Pts with primary ITP who initiated AVA (index date) July 2019 - June 2024 in the US. Pts were required to have complete medical records for 3 months (mo) prior to AVA initiation (baseline) and ≥6 mo post-index unless the Pt died. The follow-up period spanned from index until earliest of end of data availability, death, or study end. Response to AVA was defined as achievement of PC ≥30k, ≥50k, and ≥100k/µL at any time while on AVA. Time from index date to response was assessed using Kaplan-Meier analyses. PCs obtained during rescue therapy use were censored. Reduction of concomitant steroid or immunosuppressant use after AVA initiation was assessed. Results: As of the 6/30/24 database lock, 47 Pts from 7 sites were included in the analyses. At index, mean (standard deviation [SD]) age was 52.6 (17.7) years (yrs), 21/47 (45%) were female, and 39/47 (83%) were white. Median [interquartile range (IQR)] time from ITP diagnosis to index was 3.2 [0.8-10.3] yrs, and 12/47 (26%) had persistent ITP, defined as <12 mo ITP duration at index. The mean (SD) number of prior ITP treatments received per patient was 3.3 (1.8); about three-fourths (72%) of patients used a TPO-RA prior to AVA. After censoring for rescue therapy use, the median [IQR] observed PC value during baseline was 56.0 [33.3, 109.0] k/µL. Of Pts with data on reason for AVA initiation, 24/37 (65%) initiated AVA due to lack of efficacy with their prior ITP treatment. On the AVA initiation date, 13 Pts were treated with concomitant steroids and 3 with immunosuppressants. After AVA initiation, the median [IQR] duration of follow-up was 23.3 [14.5, 39.8] mo, and median [IQR] duration of AVA treatment was 18.2 [9.0, 36.3] mo. After censoring for rescue treatment, 46/47 (98%) Pts had ≥1 PC during follow-up, and response was evaluated among all Pts. 44/47 (94%), 44/47 (94%), and 42/47 (89%) Pts achieved a PC response at thresholds of ≥30k/µL, ≥50k/µL and ≥100k/µL, respectively, with a median (95% CI) time to PC response of 8.5 (7.0, 15.0) days, 9.0 (7.0, 16.0) days, and 19.5 (12.0, 32.0) days at each respective threshold. Almost all Pts (12/13) on concomitant steroids and 2/3 on immunosuppressants at AVA initiation discontinued use of these treatments post-AVA initiation. 16/47 (34%) Pts discontinued AVA during follow-up after a median [IQR] 9.0 [5.0, 14.7] mo of AVA exposure. The most common reason for AVA discontinuation was stable/improved PCs (5/16). Conclusion: Preliminary real-world results from the REAL-AVA 2.0 study are consistent with clinical trial results and provide further evidence that AVA is effective as a long-term treatment in a heavily pretreated primary ITP population receiving care in clinical practices across the US. Data collection is still underway and results in a larger sample will be reported.