ABSTRACT In March 2024, ponatinib received accelerated FDA approval for the treatment of newly diagnosed Philadelphia chromosome‐positive acute lymphoblastic leukemia (Ph + ALL) in combination with chemotherapy based on the Phase 3 PhALLCON study (NCT03589326), which demonstrated a higher rate of minimal residual disease (MRD)‐negative complete remission (CR) at the end of induction (EOI) with ponatinib (34.4%) versus imatinib (16.7%; p = 0.002). Patients received ponatinib (30 mg QD with reduction to 15 mg QD upon achievement of MRD‐negative CR at EOI) or imatinib (600 mg QD) combined with 20 cycles of reduced‐intensity chemotherapy (induction: 3 cycles; consolidation: 6 cycles; and maintenance: 11 cycles). Ponatinib pharmacokinetics (PK) were similar in patients in PhALLCON and patients in a previous population PK analysis. Bayesian re‐estimation of the previously developed population PK model adequately described PhALLCON PK data. Exposure–efficacy analyses did not identify a significant relationship between ponatinib exposure and the probability of MRD‐negative CR at EOI (p = 0.619), suggesting a consistent efficacy benefit across exposures. Ponatinib exposure was not a significant predictor of arterial occlusive events, venous thromboembolic events, thrombocytopenia, or lipase increase (p > 0.05). However, higher exposures were associated with a higher probability of hypertension (p = 0.0340) and alanine aminotransferase (ALT) increase (p = 0.0034). Dose reduction from 30 to 15 mg was predicted to decrease the odds of experiencing hypertension by 37.7% and ALT increase by 44.2%. Collectively, exposure–response analyses support a favorable benefit–risk profile of the approved ponatinib dosage (30 mg QD reduced to 15 mg QD upon achievement of MRD‐negative CR at EOI), combined with chemotherapy, for frontline treatment of Ph + ALL.

This research explores the application of marginal structural models (MSMs) in evaluating the causal treatment effect of active intervention versus control on overall survival in randomized clinical trials (RCTs) allowing for control arm patients to switch to active intervention after disease progression. When MSMs are applied in RCTs under this type of treatment switching setting, the question of interest and model specifications differ from both observational studies and from RCTs where patients in both arms are permitted to take alternative treatments after disease progression. A violation of structural positivity may result as an undesired consequence if MSM model weights are constructed using data directly from both arms. This research proposes a two-step approach to avoid this issue. Through simulation studies, it is demonstrated that the proposed approach allows for MSM to be used for analyzing survival data to detect causal active treatment effects under this one-way treatment switching setting. Additionally, estimation for the causal effect of the active intervention as the next line (post-disease progression) therapy can also be obtained from the MSM approach. A case study is presented to illustrate the application of MSMs under this type of treatment switching setting.

The presence of treatment switching in randomized controlled trials may bias estimation of causal treatment effects on outcomes such as overall survival if a standard intent-to-treat analysis approach is applied. To address this, techniques from the realm of non-experimental study methodology such as two-stage estimation (TSE) have been incorporated into the clinical trialist's toolbox. Of particular relevance to this manuscript is research exploring how TSE may be applied to settings where patients in one study arm may switch to alternative treatment so that potential bias associated with following patients after treatment switching is reduced. We contribute to the evolution of this research by extending the TSE approach so that it can appropriately account for two-arm designs where patients in both arms are allowed to switch treatments. In addition to a discussion of methodology, we have included a case study and a diversity of simulation studies supporting the statistical validity of the proposed technique.

Crossover or treatment-switching in randomized controlled trials presents notable challenges not only in the development and approval of new drugs but also poses a complex issue in their reimbursement, especially in oncology. When the investigational treatment is superior to control, crossover from control to investigational treatment upon disease progression or for other reasons will likely cause the underestimation of treatment benefit. Rank Preserving Structural Failure Time (RPSFT) and Two-Stage Estimation (TSE) methods are commonly employed to adjust for treatment switching by estimating counterfactual survival times. However, these methods may induce informative censoring by adjusting censoring times for switchers while leaving those for non-switchers unchanged. Existing approaches such as re-censoring or inverse probability of censoring weighting (IPCW) are often used alongside RPSFT or TSE to handle informative censoring, but may result in long-term information loss or suffer from model misspecification. In this paper, Kaplan-Meier multiple imputation with bootstrap procedure (KMIB) is proposed to address the informative censoring issues in adjustment methods for treatment switching. This approach can avoid information loss and is robust to model misspecification. In the scenarios that we investigate, simulation studies show that this approach performs better than other adjustment methods when the treatment effect is small, and behave similarly under other scenarios despite different switching probability. A case study in non-small cell lung cancer (NSCLC) is also provided to demonstrate the use of this method.

TOURMALINE-MM1, the only blinded randomized study in patients with relapsed and/or refractory multiple myeloma (RRMM; ≥1 prior therapy) in the last 10 years, investigated ixazomib + lenalidomide + dexamethasone (IRd) versus lenalidomide + dexamethasone (Rd). Final overall survival (OS) data were based on a median follow-up of 85 months. In RRMM trials where patients have had 1-3 relapses after initial treatment, a high proportion receive subsequent therapy. Application of salvage therapies in blinded trials and newer modes of therapy can increasingly complicate the interpretation of OS. This analysis explores the impact of subsequent therapies on OS outcomes in TOURMALINE-MM1. The inverse probability of censoring weights (IPCW) method, marginal structural model (MSM), and rank-preserving structural failure time model (RPSFTM) were utilized to adjust for confounding on OS, introduced by subsequent therapies. Analyses were conducted for the intent-totreat (ITT) population and ≥2 prior lines subgroup. Unadjusted hazard ratio (HR) for IRd versus Rd was 0.94 (95% confidence interval [CI]: 0.78-1.13) in the ITT population. After adjusting for the impact of subsequent therapies by the RPSFTM method, estimated HR for IRd versus Rd in the ITT population was 0.89 (95% CI: 0.74-1.07). Adjusting with IPCW and MSM methods also showed an improvement in HR, favoring IRd. IRd may be particularly beneficial in patients with ≥2 prior lines of therapy (IPCW and MSM HR=0.52, 95% CI: 0.30-0.88; RPSFTM HR=0.68, 95% CI: 0.51-0.91). These analyses highlight the growing challenge of demonstrating OS benefit in MM patients and the importance of assessing confounding introduced by subsequent therapies when interpreting OS.

ImportanceIn newly diagnosed Philadelphia chromosome–positive (Ph+) acute lymphoblastic leukemia (ALL), disease progression due to acquired resistance to first- or second-generation BCR::ABL1 tyrosine kinase inhibitors is common. Ponatinib inhibits BCR::ABL1 and all single-mutation variants, including T315I.ObjectiveTo compare frontline ponatinib vs imatinib in adults with newly diagnosed Ph+ ALL.Design, Setting, and ParticipantsGlobal registrational, phase 3, open-label trial in adults aged 18 years or older with newly diagnosed Ph+ ALL. From January 2019 to May 2022, eligible patients at 77 sites were randomized 2:1 to ponatinib (30 mg/d) or imatinib (600 mg/d) with reduced-intensity chemotherapy, followed by single-agent ponatinib or imatinib after the cycle 20 phase of the trial. The last date of follow-up for this analysis was August 12, 2022.InterventionPatients received ponatinib, 30 mg/d, or imatinib, 600 mg/d, with reduced-intensity chemotherapy, followed by single-agent ponatinib or imatinib after cycle 20. The ponatinib dose was reduced to 15 mg on achievement of minimal residual disease–(MRD) negative complete remission.Main Outcomes and MeasuresThe primary end point of this interim analysis was MRD-negative complete remission (≤0.01% BCR::ABL1 [MR4] centrally assessed by reverse transcriptase–quantitative polymerase chain reaction), with complete remission maintained for at least 4 weeks at the end of cycle 3. The key secondary end point was event-free survival.ResultsOf 245 patients randomized (median age, 54 years; 133 [54.3%] female), 232 (ponatinib, n = 154; imatinib, n = 78) who had p190 or p210 dominant isoforms verified by the central laboratory were analyzed for the primary end point. The MRD-negative complete remission rate (primary end point) was significantly higher with ponatinib (34.4% [53/154]) vs imatinib (16.7% [13/78]) (risk difference, 0.18 [95% CI, 0.06-0.29]; P = .002). At the data cutoff, event-free survival had not met the prespecified number of events. Median event-free survival was not reached in the ponatinib group and was 29 months in the imatinib group. The most common adverse events were similar between treatment groups. Arterial occlusive events were infrequent and comparable between groups (ponatinib, 2.5%; imatinib, 1.2%).Conclusions and RelevancePonatinib demonstrated a superior rate of MRD-negative complete remission at the end of induction vs imatinib when combined with reduced-intensity chemotherapy in adults with newly diagnosed Ph+ ALL. The safety profile of ponatinib was comparable with imatinib.Trial RegistrationClinicalTrials.gov Identifier: NCT03589326

Background: Minimal residual disease (MRD) is an established, prognostic indicator for patients with acute lymphoblastic leukemia (ALL), including Philadelphia chromosome-positive (Ph+) ALL. The objective of this study was to evaluate the association between MRD and long-term outcomes (event-free survival [EFS] and overall survival [OS]) in adult patients with Ph+ ALL receiving first-line therapy. Methods: A systematic literature review (SLR) was performed to identify eligible studies, including interventional and observational studies reporting survival outcomes by MRD status in adults ≥18 years of age with Ph+ ALL receiving first-line therapy. Key outcomes and data elements of interest were EFS, OS, and MRD or MRD-negative complete remission (CR) at end of induction (EOI). Aggregate study-level and individual patient data (IPD) meta-analyses were conducted. The IPD approach included a log-level MRD analysis to evaluate the concordance of deepening levels of molecular response with long-term EFS or OS in patients with CR and an analysis evaluating the utility of MRD-negative CR over CR alone. The analyses were conducted using frequentist and Bayesian approaches with fixed-effects and random-effects models. Kaplan-Meier method with log-rank tests was used for survival analysis. Where applicable, Cox regression method with and without adjustment for prognostic factors were applied. Results: The SLR identified 19 publications (18 unique studies), 10 (9 unique studies) of which had sufficient MRD and EFS/OS data. Nine studies (n=704) were included in the aggregate study-level analysis; 3 of the 9 studies (Phase II AP24534-11-001 [Jabbour et al. 2015], Phase II GIMEMAINCB 84344-201 [Martinelli et al. 2017], and Phase III GRAAPH-2005 RCT [Chalandon et al. 2015]) had IPD available. MRD was assessed by polymerase chain reaction in all 9 studies. Findings from the aggregate study-level meta-analysis demonstrated a significant long-term survival benefit (EFS and OS) in favor of patients with MRD-negative CR. This significant benefit was generally consistent across analysis types (base-case or sensitivity analyses), analytic models (fixed- or random-effects), and approaches (frequentist or Bayesian). Evidence from the IPD analysis, based on patients with CR, was mostly consistent with the aggregate study-level meta-analysis, supporting MRD-negative CR at the EOI as being predictive of EFS or OS. Log-level MRD analysis showed that patients who are in CR with deeper molecular response ( BCR::ABL1/ABL1 ≤0.01%) at EOI have significantly better long-term EFS and OS compared with patients with other levels of MRD (ie, BCR::ABL1/ABL1 >0.01%). This significant long-term survival benefit was also demonstrated in patients with MRD-negative CR ( BCR::ABL1/ABL1 ≤0.01%) at EOI compared with patients who were MRD-positive ( BCR::ABL1/ABL1 >0.01%) ( Table 1) or based on achievement of CR alone (regardless of BCR::ABL1/ABL1 values). Results from the IPD analysis standardized for outcome definition, with and without adjustment for prognostic factors (age, gender, white blood cell count at baseline, and stem cell transplant), were consistent with the findings from the log-level MRD analysis. The analysis showed a significant association between MRD-negative/MRD-negative CR status (ie, BCR::ABL1/ABL1 ≤0.01% threshold) at EOI with improved long-term EFS and OS. The results were significant for EFS in both the adjusted and unadjusted models. The OS results were significant only in the unadjusted model. Conclusions: These analyses indicate that a deeper molecular response at EOI results in better long-term EFS and OS; MRD-negative CR has a greater prognostic value than CR and is strongly associated with long-term EFS and OS in patients with Ph+ ALL. Acknowledgement: The authors acknowledge APHP, who provided the individualized patients data for the GRAAPH study.

Background: BCR::ABL1 tyrosine kinase inhibitors (TKIs) in combination with chemotherapy or steroids remain the standard of care in patients with newly diagnosed Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL). Most patients treated with first- or second-generation TKIs eventually experience disease progression due to treatment resistance. Ponatinib is the only currently approved pan-BCR::ABL1 inhibitory TKI that potently inhibits wild-type and single resistance mutation variants of BCR::ABL1, including T315I. Multiple studies have shown promising minimal residual disease (MRD) negativity (neg) rates and survival outcomes with ponatinib in combination with chemotherapy or chemotherapy-free regimens. PhALLCON (NCT03589326) is the first randomized study comparing frontline TKIs in adults with Ph+ ALL. The primary endpoint for PhALLCON was met, with a clinically significantly higher MRD-neg complete remission (CR) rate at end of induction (EOI) with ponatinib vs imatinib (34.4% vs 16.7%; risk difference: 0.18 [95% confidence interval (CI): 0.06‒0.29]; P=0.0021) and a manageable safety profile comparable with imatinib. Here we report subgroup efficacy analyses from PhALLCON. Methods: This global, registrational, phase 3, open-label study randomized newly diagnosed adult patients with Ph+ ALL 2:1 to receive ponatinib (30 mg once daily [QD]) or imatinib (600 mg QD) plus reduced-intensity chemotherapy through EOI (Cycles 1-3), consolidation (Cycles 4-9), and post-consolidation (Cycles 10-20). Following post-consolidation, patients continued to receive single-agent ponatinib or imatinib until disease progression or unacceptable toxicity. The composite primary endpoint was MRD-neg ( BCR:: ABL1 ≤0.01% [MR4])CR for 4 weeks at EOI. Event-free survival (EFS; any-cause death, failure to achieve CR by EOI, relapse from CR) was a key secondary endpoint. A post-hoc analysis of progression-free survival (PFS; EFS-defined events, failure to achieve MRD-neg by the end of treatment, and loss of MRD-neg) was conducted. Subgroup analyses were performed relative to baseline demographic and disease characteristics. Results: Of 245 randomized patients, 232 (ponatinib, n=154; imatinib, n=78) had baseline BCR::ABL1 p190/p210 variants verified by central lab (efficacy-evaluable population); median age was 54 years (37.1% ≥60 years). As of Aug 2022, 78 patients (ponatinib/imatinib: 68 [41.5%]/10 [12.3%]) remained on study treatment; the top 3 reasons for discontinuation were hematopoietic stem cell transplantation (HSCT; 30.5%/37.0%), adverse events (12.2%/12.3%), and lack of efficacy (7.3%/25.9%). Median follow-up in the ponatinib and imatinib arms was 20 months and 18 months, respectively. Benefit for ponatinib was observed across all subgroups analyzed ( Table). All age subgroups had higher rates of MRD-neg CR with ponatinib vs imatinib, with the greatest benefit observed in patients ≥60 years (40.0% ponatinib vs 10.3% imatinib; P=0.0005). MRD-neg CR rate was higher for ponatinib vs imatinib among those with the BCR::ABL1 p190 variant (38.6%/17.0%; P=0.0017); it was higher for the p210 variant as well, but not significantly (22.5% vs 16.0%; P=0.51). Median PFS was longer with ponatinib vs imatinib regardless of age, with the greatest difference observed in the subgroup of patients ≥60 years (22.5 months for ponatinib vs 8.3 months for imatinib; hazard ratio: 0.594 [95% CI: 0.332-1.063]). Conclusions: Ponatinib was superior to imatinib in combination with reduced-intensity chemotherapy in the front-line setting for patients with Ph+ ALL, with a clinically significantly higher MRD-neg CR rate at EOI. Benefit was observed across all subgroups, particularly for patients ≥60 years and for those with the BCR::ABL1 p190 variant.

Background: Minimal residual disease (MRD) is an established, prognostic indicator for patients with acute lymphoblastic leukemia (ALL), including Philadelphia chromosome-positive (Ph+) ALL. The objective of this study was to evaluate the association between MRD and long-term outcomes (event-free survival [EFS] and overall survival [OS]) in adult patients with Ph+ ALL receiving first-line therapy. Methods: A systematic literature review (SLR) was performed to identify eligible studies, including interventional and observational studies reporting survival outcomes by MRD status in adults ≥18 years of age with Ph+ ALL receiving first-line therapy. Key outcomes and data elements of interest were EFS, OS, and MRD or MRD-negative complete remission (CR) at end of induction (EOI). Aggregate study-level and individual patient data (IPD) meta-analyses were conducted. The IPD approach included a log-level MRD analysis to evaluate the concordance of deepening levels of molecular response with long-term EFS or OS in patients with CR and an analysis evaluating the utility of MRD-negative CR over CR alone. The analyses were conducted using frequentist and Bayesian approaches with fixed-effects and random-effects models. Kaplan-Meier method with log-rank tests was used for survival analysis. Where applicable, Cox regression method with and without adjustment for prognostic factors were applied. Results: The SLR identified 19 publications (18 unique studies), 10 (9 unique studies) of which had sufficient MRD and EFS/OS data. Nine studies (n=704) were included in the aggregate study-level analysis; 3 of the 9 studies (Phase II AP24534-11-001 [Jabbour et al. 2015], Phase II GIMEMAINCB 84344-201 [Martinelli et al. 2017], and Phase III GRAAPH-2005 RCT [Chalandon et al. 2015]) had IPD available. MRD was assessed by polymerase chain reaction in all 9 studies. Findings from the aggregate study-level meta-analysis demonstrated a significant long-term survival benefit (EFS and OS) in favor of patients with MRD-negative CR. This significant benefit was generally consistent across analysis types (base-case or sensitivity analyses), analytic models (fixed- or random-effects), and approaches (frequentist or Bayesian). Evidence from the IPD analysis, based on patients with CR, was mostly consistent with the aggregate study-level meta-analysis, supporting MRD-negative CR at the EOI as being predictive of EFS or OS. Log-level MRD analysis showed that patients who are in CR with deeper molecular response ( BCR::ABL1/ABL1 ≤0.01%) at EOI have significantly better long-term EFS and OS compared with patients with other levels of MRD (ie, BCR::ABL1/ABL1 >0.01%). This significant long-term survival benefit was also demonstrated in patients with MRD-negative CR ( BCR::ABL1/ABL1 ≤0.01%) at EOI compared with patients who were MRD-positive ( BCR::ABL1/ABL1 >0.01%) ( Table 1) or based on achievement of CR alone (regardless of BCR::ABL1/ABL1 values). Results from the IPD analysis standardized for outcome definition, with and without adjustment for prognostic factors (age, gender, white blood cell count at baseline, and stem cell transplant), were consistent with the findings from the log-level MRD analysis. The analysis showed a significant association between MRD-negative/MRD-negative CR status (ie, BCR::ABL1/ABL1 ≤0.01% threshold) at EOI with improved long-term EFS and OS. The results were significant for EFS in both the adjusted and unadjusted models. The OS results were significant only in the unadjusted model. Conclusions: These analyses indicate that a deeper molecular response at EOI results in better long-term EFS and OS; MRD-negative CR has a greater prognostic value than CR and is strongly associated with long-term EFS and OS in patients with Ph+ ALL. Acknowledgement: The authors acknowledge APHP, who provided the individualized patients data for the GRAAPH study.

398868 Background: The standard of care in patients (pts) with newly diagnosed (dx) Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia (ALL) is BCR::ABL1 tyrosine kinase inhibitors (TKIs) in combination with chemotherapy (chemo) or steroids. Treated with 1st- or 2nd-generation TKIs, pts eventually progress due to emergence of resistance. Multiple studies have reported promising minimal residual disease (MRD) negativity (neg) rates and survival outcomes with pon in combination with chemo or chemo-free regimens. PhALLCON (NCT03589326), the first randomized study comparing TKIs in pts with Ph+ALL, evaluates pon vs im in combination with reduced-intensity chemo. Methods: This phase 3 open-label trial randomized adult newly dx Ph+ALL pts 2:1 to receive pon (30 mg once daily [QD]) or im (600 mg QD) with reduced-intensity chemo through end of induction (EOI; Cycles 1–3), consolidation (Cycles 4–9), and post-consolidation (Cycles 10–20). After Cycle 20, pts received single-agent pon or im until disease progression or unacceptable toxicity. The composite primary endpoint was MRD-neg ( BCR:: ABL1 ≤0.01% ) complete remission (CR) for 4 weeks at EOI. Event-free survival (EFS: any cause death, failure to achieve CR by EOI, relapse from CR) was a key secondary endpoint. Results: 245 pts were randomized to pon (n=164) or im (n=81); median age was 54 y (37% ≥60 y). At data cutoff (Aug 2022), 78 pts (pon vs im: 42% vs 12%) were on study treatment; the top 3 reasons for discontinuation were hematopoietic stem cell transplantation (31% vs 37%), adverse events (12% vs 12%), and lack of efficacy (7% vs 26%). Median follow-up was 20 mo vs 18 mo (pon vs im). The primary endpoint was met (Table) by significantly higher MRD-neg CR rate for pon vs im (34.4% vs 16.7%; p=0.0021). Survival data were not mature; however, the median EFS was reached in im and not in pon, with a trend toward improvement (HR=0.652, 95% CI 0.385–1.104). Time to treatment failure reported an improvement as well (HR=0.455). The treatment-emergent adverse event (TEAE) rates (any grade [Gr] and Gr3/4/5) were comparable between treatment arms. Arterial occlusive events (AOEs) were infrequent and similar between the arms (Table). Conclusions: Pon was superior to im in combination with reduced-intensity chemo in pts with newly dx Ph+ALL, with a significantly higher MRD-neg CR rate at the EOI. Pon was associated with deeper and more durable responses, with a trend toward improved EFS and comparable safety vs im. Clinical trial information: NCT03589326 . [Table: see text]

Topic: 2. Acute lymphoblastic leukemia - Clinical Background: The standard of care in patients with newly diagnosed Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia (ALL) is BCR::ABL1 tyrosine kinase inhibitors (TKIs) in combination with chemotherapy or steroids. Treated with first- or second-generation TKIs, patients eventually progress due to emergence of resistance. Multiple studies have reported promising minimal residual disease (MRD) negativity (neg) rates and survival outcomes with ponatinib in combination with chemotherapy or chemotherapy-free regimens. Aims: PhALLCON (NCT03589326), the first randomized study comparing TKIs in patients with Ph+ ALL, evaluates ponatinib versus imatinib in combination with reduced-intensity chemotherapy. Methods: This phase 3 open-label study randomized newly diagnosed Ph+ ALL adult patients 2:1 to receive ponatinib (30 mg once daily [QD]) or imatinib (600 mg QD) with reduced-intensity chemotherapy through end of induction (EOI), consolidation, and post-consolidation. After post-consolidation, patients received single-agent ponatinib or imatinib until disease progression or unacceptable toxicity. The composite primary endpoint was MRD-neg (BCR::ABL1 ≤0.01%) complete remission (CR) for 4 weeks at EOI. Event-free survival (EFS: any-cause death, failure to achieve CR by EOI, relapse from CR) was a key secondary endpoint. Results: A total of 245 pts were randomized to ponatinib (n=164) or imatinib (n=81); median age was 54 years (37% ≥60 years). At data cutoff (Aug 2022), 78 patients (ponatinib vs imatinib: 42% vs 12%) were on study treatment; the top 3 reasons for discontinuation were hematopoietic stem cell transplantation (30% vs 37%), adverse events (12% vs 12%), and lack of efficacy (7% vs 26%). Median follow-up was 20 months vs 18 months (ponatinib vs imatinib). The primary endpoint was met (Table), with a significantly higher MRD-neg CR rate at EOI for ponatinib vs imatinib (34% vs 17%; P=0.0021). Additionally, MRD-neg rate regardless of CR at EOI was significantly higher for ponatinib vs imatinib (43% vs 21%; P=0.0017). Median duration of MRD-neg and time to treatment failure were not reached for ponatinib and were 20.9 months and 21.9 months, respectively, for imatinib. EFS data were not mature; however, the median EFS was reached in imatinib and not in ponatinib, with a trend toward improvement (hazard ratio [HR] 0.65, 95% confidence interval [CI] 0.39–1.10). The treatment-emergent adverse event (TEAE) rates (any-grade and Grade 3/4/5) were comparable between treatment arms. Most common any-grade hematologic TEAEs were anemia (ponatinib 72%, imatinib 67%) and platelet count decrease (ponatinib 68%, imatinib 69%). The most common Grade 3/4 nonhematologic TEAEs were headache (ponatinib and imatinib 43%) and nausea (ponatinib 35%, imatinib 50%). Incidence of arterial occlusive events (AOEs) were infrequent and similar between the arms (Table). Summary/Conclusion: Ponatinib was superior to imatinib in combination with reduced-intensity chemotherapy in the front-line setting for patients with Ph+ ALL, with a significantly higher MRD-neg CR rate at EOI. Ponatinib was associated with deeper and more durable responses, with a trend toward improved EFS and comparable safety vs imatinib.Keywords: Ph+ ALL

BACKGROUND:The TOURMALINE-MM4 trial demonstrated a significant and clinically meaningful progression-free survival (PFS) benefit with ixazomib versus placebo as postinduction maintenance in nontransplant, newly-diagnosed multiple myeloma patients, with a manageable and well-tolerated toxicity profile. MATERIALS AND METHODS:In this subgroup analysis, efficacy and safety were assessed by age (< 65, 65-74, and ≥ 75 years) and frailty status (fit, intermediate-fit, and frail). RESULTS:In this analysis, PFS benefit with ixazomib versus placebo was seen across age subgroups, including patients aged < 65 years (hazard ratio [HR], 0.576; 95% confidence interval [CI], 0.299-1.108; P = .095), 65-74 years (HR, 0.615; 95% CI, 0.467-0.810; P < .001), and ≥ 75 years (HR, 0.740; 95% CI, 0.537-1.019; P = .064). PFS benefit was also seen across frailty subgroups, including fit (HR, 0.530; 95% CI, 0.387-0.727; P < .001), intermediate-fit (HR, 0.746; 95% CI, 0.526-1.058; P = .098), and frail (HR, 0.733; 95% CI, 0.481-1.117; P = .147) patients. With ixazomib versus placebo, rates of grade ≥ 3 treatment-emergent adverse events (TEAEs; 28-44% vs. 10-36%), serious TEAEs (15-29% vs. 3-29%), and discontinuation due to TEAEs (7-19% vs. 5-11%) were higher or similar across age and frailty subgroups, and generally somewhat higher in older age groups and intermediate-fit/frail patients in both arms. Treatment with ixazomib versus placebo did not adversely affect patient-reported quality-of-life scores across age and frailty status subgroups. CONCLUSION:Ixazomib is a feasible and effective maintenance option for prolonging PFS across this heterogeneous patient population.

398868 Background: The standard of care in patients (pts) with newly diagnosed (dx) Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia (ALL) is BCR::ABL1 tyrosine kinase inhibitors (TKIs) in combination with chemotherapy (chemo) or steroids. Treated with 1st- or 2nd-generation TKIs, pts eventually progress due to emergence of resistance. Multiple studies have reported promising minimal residual disease (MRD) negativity (neg) rates and survival outcomes with pon in combination with chemo or chemo-free regimens. PhALLCON (NCT03589326), the first randomized study comparing TKIs in pts with Ph+ALL, evaluates pon vs im in combination with reduced-intensity chemo. Methods: This phase 3 open-label trial randomized adult newly dx Ph+ALL pts 2:1 to receive pon (30 mg once daily [QD]) or im (600 mg QD) with reduced-intensity chemo through end of induction (EOI; Cycles 1–3), consolidation (Cycles 4–9), and post-consolidation (Cycles 10–20). After Cycle 20, pts received single-agent pon or im until disease progression or unacceptable toxicity. The composite primary endpoint was MRD-neg ( BCR:: ABL1 ≤0.01% ) complete remission (CR) for 4 weeks at EOI. Event-free survival (EFS: any cause death, failure to achieve CR by EOI, relapse from CR) was a key secondary endpoint. Results: 245 pts were randomized to pon (n=164) or im (n=81); median age was 54 y (37% ≥60 y). At data cutoff (Aug 2022), 78 pts (pon vs im: 42% vs 12%) were on study treatment; the top 3 reasons for discontinuation were hematopoietic stem cell transplantation (31% vs 37%), adverse events (12% vs 12%), and lack of efficacy (7% vs 26%). Median follow-up was 20 mo vs 18 mo (pon vs im). The primary endpoint was met (Table) by significantly higher MRD-neg CR rate for pon vs im (34.4% vs 16.7%; p=0.0021). Survival data were not mature; however, the median EFS was reached in im and not in pon, with a trend toward improvement (HR=0.652, 95% CI 0.385–1.104). Time to treatment failure reported an improvement as well (HR=0.455). The treatment-emergent adverse event (TEAE) rates (any grade [Gr] and Gr3/4/5) were comparable between treatment arms. Arterial occlusive events (AOEs) were infrequent and similar between the arms (Table). Conclusions: Pon was superior to im in combination with reduced-intensity chemo in pts with newly dx Ph+ALL, with a significantly higher MRD-neg CR rate at the EOI. Pon was associated with deeper and more durable responses, with a trend toward improved EFS and comparable safety vs im. Clinical trial information: NCT03589326 . [Table: see text]

2506 Background: SUMOylation is a post-translational modification with a role in limiting type 1 interferon (IFN-1)-dependent immune responses. Subasumstat is a small-molecule inhibitor of SUMOylation with the potential to increase antitumor immunity and overcome tumor resistance to checkpoint inhibitors (CPI) by inducing IFN-1 signaling. Preclinical data suggest that subasumstat enhances antigen cross-presentation, promoting T cell dependent antitumor responses; subasumstat plus an anti-PD-1 CPI has shown synergistic tumor growth inhibition and activation of CD8+ T cells and natural killer cells in syngeneic mouse models. We report data from the dose escalation part of a phase 1b study of subasumstat with pembrolizumab in pts with relapsed/refractory, CPI-exposed, non-squamous non-small-cell lung cancer (NSCLC) or microsatellite-stable colorectal cancer (MSS-CRC). Methods: Pts received escalating doses (40, 60, 90, and 120 mg) of subasumstat IV in 3 dosing schedules: days 1 and 8 (QW), days 1, 4, 8, and 11 (BIW), or days 1, 8, and 15 (90 mg only) of 21-day cycles, plus pembrolizumab 200 mg IV on day 1 of each cycle for 2 years or until disease progression or unacceptable toxicity. Dose escalation was guided by Bayesian optimal interval design. Phase 1b primary objectives were safety, tolerability, and the recommended phase 2 dose of subasumstat with pembrolizumab. Results: As of October 13, 2021, 43 (35 MSS-CRC; 8 NSCLC) pts had received ≥1 dose of subasumstat (22 BIW [40–120 mg]; 15 QW [90 –120 mg]; 6 on days 1, 8, 15 [90 mg)]. Median number of treatment cycles was 3; 28 (65%) pts had discontinued treatment, 21 (49%) due to progressive disease. Median age was 58 years (range 34–77); 56% of pts were male. One pt had a dose-limiting toxicity of grade 3 angioedema at 120 mg BIW. The maximum tolerated dose was not identified. Treatment-emergent adverse events (TEAEs) occurred in 38 (88%) pts; subasumstat-related TEAEs occurred in 34 (79%) pts, and included chills in 20 (47%), pyrexia in 16 (37%), fatigue in 9 (21%), anemia in 6 (14%), and stomatitis in 5 pts (12%; 3 [50%] in the 120 mg BIW cohort). Grade ≥3 TEAEs occurred in 24 (56%) pts; subasumstat-related grade ≥3 TEAEs reported in 10 (23%) pts included anemia, pyrexia, and increased aspartate aminotransferase (2 [5%] pts each). Pharmacokinetic activity of subasumstat was linear and decreased in a tri-phasic manner. Subasumstat exerted pharmacodynamic activity including target engagement, SUMOylation inhibition and increased IFN-1 signaling. Partial responses were observed at ≥40 mg dose levels in pts with NSCLC and MSS-CRC. Conclusions: Subasumstat plus pembrolizumab showed a favorable safety profile and promising anti-tumor activity in pre-treated NSCLC and MSS-CRC pts. Updated data will be presented at the meeting. Subasumstat plus pembrolizumab is currently in phase 2 clinical development (NCT04381650). Clinical trial information: NCT04381650.

This research focuses on the bias and type I error control issues when the marginal structural models (MSMs) are applied to evaluate the causal survival benefits of active intervention versus control in randomized clinical trials (RCTs) with treatment switching after disease progression. When MSMs are applied in the RCT setting, the question of interest, model specifications, strategies for type I error control, bias reduction, etc. differ somewhat from those for observational studies. This manuscript discusses the approaches used to accommodate these differences. Through Monte Carlo simulations and a case study, our research demonstrates that, with sufficient attention paid to issues applicable to RCTs in particular, MSMs may perform better than the inverse probability of censoring weighting (IPCW) method in analyzing the survival endpoint in RCTs with treatment switching because more information is used by the MSM.

Measurable residual disease (MRD) evaluation may help to guide treatment duration in multiple myeloma (MM). Paradoxically, limited longitudinal data exist on MRD during maintenance. We investigated the prognostic value of MRD dynamics in 1280 transplant -eligible and-ineligible patients from the TOURMALINE-MM3 and-MM4 randomized placebo-controlled phase 3 studies of 2-year ixazomib maintenance. MRD status at randomization showed independent prognostic value (median progression-free survival [PFS], 38.6 vs 15.6 months in MRD- vs MRD+ patients; HR, 0.47). However, MRD dynamics during maintenance provided more detailed risk stratification. A 14-month landmark analysis showed prolonged PFS in patients converting from MRD+ to MRD- status vs those with persistent MRD+ status (76.8% vs 27.6% 2-year PFS rates). Prolonged PFS was observed in patients with sustained MRD- status vs those converting from MRD- to MRD+ status (75.0% vs 34.2% 2-year PFS rates). Similar results were observed at a 28 -month landmark analysis. Ixazomib maintenance vs placebo improved PFS in patients who were MRD+ at randomization (median, 18.8 vs 11.6 months; HR, 0.65) or at the 14-month landmark (median, 16.8 vs 10.6 months; HR, 0.65); no difference was observed in patients who were MRD-. This is the largest MM population undergoing yearly MRD evaluation during maintenance reported to date. We demonstrate the limited prognostic value of a single-time point MRD evaluation, because MRD dynamics over time substantially impact PFS risk. These findings support MRD- status as a relevant end point during maintenance and confirm the increased progression risk in patients converting to MRD+ from MRD- status.

BackgroundSUMOylation is a post-translational modification that serves as an important modulator of immune responses via its role in constraining the type I interferon (IFN-1) response. TAK-981 is a small molecule that inhibits SUMOylation and increases IFN-1-dependent innate immune responses with the potential to enhance adaptive immunity. Here, we report dose-escalation data from a TAK-981 Phase 1/2 clinical study (NCT03648372), the first clinical data for a SUMOylation inhibitor.MethodsAdults with advanced/metastatic solid tumors or relapsed/refractory lymphomas received TAK-981 IV twice-weekly (BIW; days 1, 4, 8, 11) or once-weekly (QW; days 1, 8) in 21-day cycles. Dose escalation was guided by a Bayesian Logistic Regression Model (BLRM) with overdose control, plus available pharmacokinetic/pharmacodynamic (PK/PD) data. Phase 1 objectives were to determine TAK-981 safety/tolerability and establish the recommended phase 2 dose (RP2D).ResultsSeventy-six patients received TAK-981 at 10 dose levels (3–40 mg BIW; 60–120 mg QW/BIW). Median age was 61 years (range, 38–79); 42 (55.3%) patients were female. Four dose-limiting toxicities were seen in 62 evaluable patients (transient grade 3 ALT/AST elevation, 60 mg BIW; grade 3 pneumonitis, 90 mg BIW; grade 3 stomatitis and grade 3 cognitive disturbance, 120 mg BIW). Per BLRM, 120 mg BIW was determined to be the maximum tolerated dose. At data cut-off, median treatment duration was 2 cycles (range, 1–12); 13 (17.1%) patients were ongoing. table 1 summarizes TAK-981 safety. The most common (≥20%) treatment-emergent adverse events (TEAEs) were fatigue (42.1%), nausea (39.5%), headache (31.6%), diarrhea (28.9%), pyrexia (27.6%), vomiting (23.7%), decreased appetite (22.4%). Common (≥5%) grade ≥3 TEAEs were hypokalemia (9.2%), anemia (7.9%), lymphocyte count decreased (6.6%), abdominal pain (5.3%). Grade 2 cytokine release syndrome was reported in 4 (5.2%) patients; symptoms resolved within 12–24 hours with supportive oxygen and/or IV fluids. One partial response was observed at 40 mg TAK-981 BIW in a patient with relapsed/refractory HER2-negative, hormone receptor-positive breast cancer. TAK-981 exhibited linear PK, with approximately dose-proportional exposure and a mean terminal half-life of 3.8–10.8 hours at ≥60 mg. Evidence of dose-dependent target engagement (figure 1), and PD (figures 2–4) in blood were observed. The single-agent TAK-981 RP2D was 90 mg BIW.Abstract 476 Table 1Summary of TAK-981 safety profileAbstract 476 Figure 1PD in patients receiving TAK-981 on the BIW schedule: target engagement.Blood samples were collected on Cycle 1 Day 1 pre-dose and at multiple timepoints after TAK-981 administration. Target engagement in T cells was detected by flow cytometry with an antibody recognizing the TAK-981-SUMO adduct formed during the inhibition of the SUMO-activating enzyme by TAK-981; Cycle 1 Day 1 signal increased at 1 hour post-end-of-infusion compared to the background level observed pre-dose.Abstract 476 Figure 2PD in patients receiving TAK-981 on the BIW schedule: SUMOylation.SUMOylation in T cells, detected by flow cytometry with an antibody recognizing SUMO2/3, decreased at 1 hour post-end-of-infusion on Cycle 1 Day 1 compared to pre-dose, indicating that fewer SUMO2/3 chains are formed when the SUMO-activating enzyme is inhibited.Abstract 476 Figure 3PD in patients receiving TAK-981 on the BIW schedule: upregulation of CXCL10 expression.Upregulation of mRNA levels of CXCL10, an IFN-I-regulated gene, in peripheral blood. Gene expression was measured using Nanostring nCounter at Cycle 1 Day 1 pre-dose and at several timepoints post-dose. Data for maximum increase at 8 or 24 hours, relative to pre-dose, is shown.Abstract 476 Figure 4PD in patients receiving TAK-981 on the BIW schedule: NK cell activation.NK cell activation in peripheral blood measured by flow cytometry. Percentage of CD69-positive NK cells at Cycle 1 Day 1 pre-dose and at 24 hours post-end-of-infusion is shown by patient for each dose.ConclusionsThe data generated in this study support continued TAK-981 development for treatment of solid tumors and lymphoma. The Phase 2 study expansion is ongoing in patients with advanced/metastatic non-small-cell lung, cervical, and colorectal cancer, and in relapsed/refractory non-Hodgkin lymphoma.Trial RegistrationClinical Trial identification: ClinicalTrials.gov. Identifier: NCT03648372Ethics ApprovalThe study was approved by the Institutional Review Board or Institutional Ethics Committee of all participating institutions

Background: Ponatinib (PON) is active against native BCR::ABL1 and all identified single-resistance mutations, including T315I. In newly diagnosed patients with Ph+ ALL treated with first- or second-generation tyrosine kinase inhibitors (TKIs), development of secondary resistance mutations in BCR::ABL1 is strongly associated with disease progression. Use of first-line PON in Ph+ ALL may decrease likelihood of these mutations and provide deeper, more durable responses. A Phase 2 study of PON in combination with chemotherapy in patients with newly diagnosed Ph+ ALL reported improved long-term outcomes with a 5-year event free survival and overall survival of 67% and 71%, respectively. Aims: This study aims to compare efficacy and safety of first-line PON versus imatinib with reduced-intensity chemotherapy in patients with newly diagnosed Ph+ or BCR::ABL1–positive ALL (p190/p210 transcript type). Methods: PhALLCON (NCT03589326) is a Phase 3, open-label, parallel-assignment, randomized study. Patients remain on treatment until relapse from complete remission (CR), have progressive disease, have unacceptable toxicity, withdraw consent, proceed to hematopoietic stem cell transplant (HSCT), complete study (20 cycles), are deceased, or sponsor terminates study. The trial will enroll ≈230 evaluable patients (aged ≥18 years) with ECOG performance status ≤2, randomized 2:1 to PON 30 mg/d or imatinib 600 mg/d orally, with reduced-intensity chemotherapy in induction (Cycles 1–3), consolidation (Cycles 4–9), and maintenance (Cycles 10–20). Enrollment is defined as randomized to study drug. Primary endpoint is minimal residual disease (MRD)-negative (BCR::ABL1/ABL1 ≤0.01%) CR at end of induction (≈3 months). Key secondary endpoint is EFS, defined as dates of randomization until death (any cause), failure to achieve MRD-negative CR by end of induction, or relapse from CR. Other secondary endpoints include CR/incomplete blood count recovery rates, molecular response rates, MRD-negative CR duration, primary induction failure, overall response rate, CR duration, time to treatment failure, overall survival, and safety, including arterial occlusive/venous thromboembolic events. After induction, durations will be measured from first report. Other analyses include a subgroup analysis of patients with/without HSCT and an exploratory analysis by mutation status. Results: First patient was randomized into the study in January 2019 with enrollment ongoing in 18 countries at 117 initiated sites; ≈226 patients were randomized as of February 2022. Summary/Conclusion: This is the only registrational RCT Phase 3 study in Ph+ ALL, and it compares efficacy and safety of the only third-generation pan-inhibitor BCR::ABL1 TKI PON with first-generation imatinib in combination with chemotherapy in the first-line setting for adult patients with Ph+ ALL. This abstract is an encore from the Society of Hematologic Oncology 2021 Annual Meeting.

TPS2667 Background: SUMOylation, a posttranslational modification analogous to ubiquitination, attaches a small, ubiquitin-like modifier (SUMO) to target proteins. SUMOylation plays a central role in regulating type I interferon (IFN-I)-dependent innate response and functions to constrain the innate immune response, which can impair tumor immune surveillance. TAK-981 is a first-in-class, small-molecule inhibitor of SUMO-activating enzyme subunit 2 (SAE2). Inhibition of SAE2 by TAK-981 disrupts SUMOylation, thereby allowing innate immune system activation. In ex vivo assays, TAK-981 increased phagocytic activity of monocyte-derived macrophages, increased natural killer cell cytotoxicity, and induced markers of dendritic cell activation and maturation via IFN-I signaling. In syngeneic mouse models, TAK-981 resulted in antitumor activity, including complete remissions, and a sustained, protective antitumor immune response. Methods: This first-in-human study of single-agent TAK-981 comprises two parts. Phase 1 primary objectives are to determine safety and tolerability, and to select a recommended phase 2 dose (RP2D); secondary objectives are to assess preliminary antitumor activity, characterize pharmacokinetics (PK), and explore pharmacodynamic (PD) biomarkers. This phase will enroll ̃70 pts with untreatable locally advanced or metastatic solid tumors or RR lymphoma. The phase 2 primary objective is to evaluate preliminary efficacy at the RP2D in ̃132 pts with non-squamous non-small cell lung cancer, cervical cancer, microsatellite-stable colorectal cancer, or CD20+ RR diffuse large B-cell lymphoma or follicular lymphoma. Pts receive TAK-981 via a 1-hour intravenous infusion on days 1, 4, 8, and 11 in 21-day cycles until unacceptable toxicity, pt withdrawal, or death. Dose escalation is proceeding from 3 mg, guided by an adaptive 3+3 design combined with Bayesian logistic regression modelling with overdose control, plus consideration of other safety, clinical, PK, and PD data. The RP2D will be based on the maximum tolerated dose (MTD) or on a biologically effective dose (BED) that is ≤MTD. The BED is defined as a dose at which there is evidence of drug-target engagement and inhibition of SUMOylation, plus: induction of cytokines/chemokines and/or IFN-I signature in tumor or blood; evidence of increased T cell infiltration in tumor; or antitumor activity. PK/PD modeling in the BED range is ongoing and will be used in RP2D determination. Clinical trial information: NCT03648372.