Improved long-term tolerability with asciminib (ASC) vs investigator-selected (IS) tyrosine kinase inhibitors (TKIs) in patients (pts) with newly diagnosed chronic myeloid leukemia in chronic phase (CML-CP): Week 96 exploratory analysis of the phase 3 ASC4FIRST trial Free

Introduction Long-term CML treatment (Tx) requires assessing adverse event (AE) burden over time to optimize safety, tolerability, and efficacy. ASC4FIRST (NCT04971226) results demonstrated superior efficacy and favorable safety/tolerability of ASC vs IS-TKIs in newly diagnosed CML-CP. A prior report showed a lower risk of discontinuation due to AEs with ASC vs second-generation (2G) TKIs in a time to Tx discontinuation due to AEs (TTDAE) analysis (hazard ratio, 0.46; 95% CI, 0.215-0.997), suggesting better tolerability with ASC. We report exploratory post hoc analyses, including an innovative analysis of AE-free days, further evaluating the tolerability of ASC vs IS-TKI (imatinib [IMA]/2G TKIs) by the wk 96 analysis cutoff (Oct 22, 2024).

Methods Adults with newly diagnosed CML-CP were randomized 1:1 to receive ASC or IS-TKI (at label dose), stratified by ELTS risk category and prerandomization IS-TKI (IMA/2G TKIs). Dose modifications occurred per protocol for ASC and at investigator's discretion for IS-TKIs.

All reported AEs occurred on Tx or ≤30 days after last dose. Exploratory tolerability analyses included frequency/grade/type of AEs; relative dose intensity; rate of dose adjustment, interruption, or discontinuation; percentage of AE-free days (number of days pt was on Tx without any-grade AEs divided by Tx duration in days, censored at the wk 96 visit; a value of 100% indicates no AEs were experienced on Tx); and pt-reported outcome (PRO) measures (PRO-CTCAE and FACIT GP5).

Results Safety analyses included all pts who received Tx in IMA (ASC^IMA [n=100]; IS-TKI^IMA [n=99]) and 2G TKI (ASC^2G [n=100]; IS-TKI^2G [n=102]) strata. Median follow-up was similar across groups (ASC^IMA [25.1 mo]; IS-TKI^IMA [24.3 mo]; ASC^2G [28.2 mo]; IS-TKI^2G [27.7 mo]). More pts were continuing Tx at cutoff with ASC^IMA (83.0%) vs IS-TKI^IMA (52.5%) and ASC^2G (81.0%) vs IS-TKI^2G (69.6%). More pts had relative dose intensity of >90% with ASC^IMA (86.0%) vs IS-TKI^IMA (79.8%) and ASC^2G (88.0%) vs IS-TKI^2G (68.6%).

The proportion of pts with dose reductions was lower with ASC^IMA (n=19, 19.0%) vs IS-TKI^IMA (n=23, 23.2%) and ASC^2G (n=18, 18.0%) vs IS-TKI^2G (n=56, 54.9%).

A similar number of pts with ASC^IMA (47.0%) vs IS-TKI^IMA (47.5%) and fewer pts with ASC^2G (46.0%) vs IS-TKI^2G (63.7%) had dose interruptions for any reason (included AEs, dosing/dispensing error, physician/pt decision, and technical problems); interruptions due to AEs were fewer with ASC vs IS-TKIs (ASC^IMA [33.0%] vs IS-TKI^IMA [37.4%]; ASC^2G [33.0%] vs IS-TKI^2G [51.0%]).

Less pts with ASC vs IS-TKIs had dose adjustment and/or interruption (ASC^IMA [13.0%] vs IS-TKI^IMA [18.2%]; ASC^2G [14.0%] vs IS-TKI^2G [31.4%]) and discontinuation (ASC^IMA [3.0%] vs IS-TKI^IMA [6.1%]; ASC^2G [1.0%] vs IS-TKI^2G [7.8%]) due to grade 1/2 nonhematologic AEs, most common (≥3%) being diarrhea, fatigue, COVID-19, nausea, and pleural effusion. A lower proportion of pts with ASC vs IS-TKIs discontinued due to grade ≥3 nonhematologic AEs (ASC^IMA [2.0%] vs IS-TKI^IMA [4.0%]; ASC^2G [2.0%] vs IS-TKI^2G [3.9%]). Dose adjustment and/or interruption due to grade ≥3 nonhematologic AEs occurred in 17.0% vs 8.1% of pts with ASC^IMA vs IS-TKI^IMA and 11.0% vs 17.6% with ASC^2G vs IS-TKI^2G.

Pts with ASC vs IS-TKIs had a higher median percentage of AE-free days by wk 96 (ASC^IMA [15.7%] vs IS-TKI^IMA [3.5%]; ASC^2G [22.6%] vs IS-TKI^2G [4.3%]) and vs individual 2G TKIs (nilotinib [13.5%]; dasatinib [4.2%]; bosutinib [0.1%]) in this arm. Pts with ASC had a higher proportion of symptomatic (nonhematologic, nonlaboratory AEs) AE–free days (ASC^IMA [31.2%] vs IS-TKI^IMA [9.9%]; ASC^2G [34.2%] vs IS-TKI^2G [15.7%]; and vs individual 2G TKIs: nilotinib [30.3%]; dasatinib [8.5%]; bosutinib [0.1%]).

When analyzing maximum scores in PRO-CTCAE reported from baseline to wk 96, symptoms reported with ASC vs IS-TKIs were generally less frequent and less severe, with a smaller impact on daily life. At wk 96, more pts reported being not at all bothered by Tx side effects with ASC vs IS-TKIs per FACIT GP5 (67.0% vs 46.1%).

Conclusions Pts with ASC had more days free from AEs, especially symptomatic AEs, and reported a lower symptom burden. Effective relative dose intensity (>90%) was higher with ASC vs IS-TKIs, with generally fewer pts requiring dose reduction, interruption, or discontinuation. These results from ASC4FIRST further support ASC'sfavorable tolerability vs all current frontline TKIs.