Ibrutinib Research Articles

Toxicity and Dermatokinetic Analysis of Ibrutinib in Human Skin Models

Background/Objectives: Ibrutinib (IBR) is a tyrosine kinase inhibitor under investigation in preclinical and clinical settings as an alternative treatment for melanoma. Nevertheless, the limited oral bioavailability of IBR and the need for high doses of the drug to kill melanoma cells are major drawbacks for this purpose. Considering that melanoma is restricted to the skin at early stages, the topical application of IBR might constitute an effective and safer administration route. In this study, we determined IBR’s toxicity and dermatokinetics using human primary cells and human organotypic skin explant cultures (hOSECs). Methods: After demonstrating that human primary fibroblasts and keratinocytes present IBR target genes, the cytotoxicity of the drug was determined using the MTT and annexin V/PI staining assays. IBR toxicity in the skin was assessed using the TTC assay, and the irritation potential was established using histological assessment. Finally, IBR cutaneous permeation was assessed ex vivo to determine the drug dermatokinetics. Results: Our findings reveal that IBR exerts dose-dependent toxicity towards skin cells, presenting an IC50 in the same range as melanoma cells. The topical application of the drug successfully reduced irritation and toxicity in the skin, and the drug was shown to successfully permeate the stratum corneum and reach the viable skin layers in therapeutic concentrations. Conclusions: Overall, our data encourage the topical application of IBR to treat melanoma, paving the way for future studies in this theme.

Characterization of ibrutinib's effects on the morphology, proliferation, phenotype, viability, and anti-inflammatory potential of adipose-derived mesenchymal stromal cells

Ibrutinib (IB) is a tyrosine kinase inhibitor (TKI) that has immunomodulatory action and can be used as second-line therapy for steroid-refractory or steroid-resistant chronic Graft versus Host Disease (cGVHD). Mesenchymal stromal cells (MSCs) are distributed throughout the body and their infusion has also been explored as a second-line therapeutic alternative for the treatment of cGVHD. Considering the currently unknown effects of IB on endogenous MSCs, as well as the possible combined use of IB and MSCs for cGVHD, we investigated whether adipose tissue-derived MSCs present IB-targets, as well as the consequences of treating MSCs with this drug, regarding cell viability, proliferation, phenotype, and anti-inflammatory potential. Interestingly, we show for the first time that MSCs express several IB target genes. Also of note, the treatment of such cells with this TKI elevated the levels of CD90 and CD105 surface proteins, as well as VCAM-1. Furthermore, IB-treated MSCs presented increased mRNA expression of the anti-inflammatory genes PD-L1, TSG-6, and IL-10. However, continued exposure to IB, even at low doses, compromised the viability of MSCs. These data indicate that the use of IB can stimulate an anti-inflammatory profile in MSCs, but also that a continued exposure to IB can compromise MSC viability over time.

Nanomodulators targeting endothelial WNT and pericytes to reversibly open the blood–tumor barrier for boosted brain tumor therapy

The blood–brain barrier (BBB)/blood–tumor barrier (BTB) impedes brain entry of most brain-targeted drugs, whether they are water-soluble or hydrophobic. Endothelial WNT signaling and neoplastic pericytes maintain BTB low permeability by regulating tight junctions. Here, we proposed nitazoxanide (NTZ) and ibrutinib (IBR) co-loaded ICAM-1-targeting nanoparticles (NI@I-NPs) to disrupt the BTB in a time-dependent, reversible, and size-selective manner by targeting specific ICAM-1, inactivating WNT signaling and depleting pericytes in tumor-associated blood vessels in breast cancer brain metastases. At the optimal NTZ/IBR mass ratio (1:2), BTB opening reached the optimum effect at 48–72 h without any sign of intracranial edema and cognitive impairment. The combination of NI@I-NPs and chemotherapeutic drugs (doxorubicin and etoposide) extended the median survival of mice with breast cancer brain metastases. Targeting BTB endothelial WNT signaling and tumor pericytes via NI@I-NPs could open the BTB to improve chemotherapeutic efficiency against brain metastases.

Ibrutinib topical delivery for melanoma treatment: The effect of nanostructured lipid carriers’ composition on the controlled drug skin deposition

Melanoma is responsible for more than 80% of deaths related to skin diseases. Ibrutinib (IBR), a Bruton's tyrosine kinase inhibitor, has been proposed to treat this type of tumor. However, its low solubility, extensive first-pass effect, and severe adverse reactions with systemic administration affect therapeutic success. This study proposes developing and comparing the performance of two compositions of nanostructured lipid carriers (NLCs) to load IBR for the topical management of melanomas in their early stages. Initially, the effectiveness of IBR on melanoma proliferation was evaluated in vitro, and the results confirmed that the drug reduces the viability of human melanoma cells by inducing apoptosis at a dose that does not compromise dermal cells. Preformulation tests were then conducted to characterize the physical compatibility between the drug and the selected components used in NLCs preparation. Sequentially, two lipid compositions were used to develop the NLCs. Formulations were then characterized and subjected to in vitro release and permeation tests on porcine skin. The NLCs containing oleic acid effectively controlled IBR release over 24 h compared to the NLCs composed of pomegranate seed oil. Furthermore, the nanoparticles acted as permeation enhancers, increasing the fluidity of the lipids in the stratum corneum, as determined by EPR spectroscopy, which stimulated the IBR penetration more profoundly into the skin. However, the NLCs composition also influenced the permeation promotion factor. Thus, these findings emphasize the importance of the composition of NLCs in controlling and increasing the skin penetration of IBR and pave the way for future advances in melanoma therapy.

Development and Validation of a Chromatographic Method for Ibrutinib Determination in Human and Porcine Skin

Ibrutinib (IBR) is a tyrosine kinase inhibitor investigated for treating solid and non-solid tumors. Considering the advantages that a topical application of IBR could generate in terms of dose reduction and side effects in skin cancer treatment, this paper presents a simple and selective HPLC method for determining IBR concentration in in vitro skin permeation studies to support the development of topical formulations. The method uses a reversed-phase C18 column and a mobile phase composed of acetonitrile and 0.01 mol/L phosphoric acid at pH 3.5 (35:65 v/v), flowing at 1.0 mL/min. The oven temperature was set at 35 °C, the injection volume was 20 μL, and UV drug detection was performed at 259 nm. The validation procedure certified that this method was selective for IBR determination even when extracted from human or porcine skin matrices. The method was linear over a range of 0.2 to 15.0 μg/mL, precise, robust, and accurate, with recovery rates from the skin layers higher than 89.5 ± 5.9% for the porcine skin and higher than 92.0 ± 0.2% for the human skin. The limits of detection and quantification were 0.01 and 0.02 μg/mL, respectively. The method showed, therefore, to be adequate for use in further skin permeation studies employing IBR topical formulations.

Network meta-analysis of novel targeted therapies for relapsed/refractory chronic lymphocytic leukemia.

The recent development of new antileukemic therapies (anti-CD20 monoclonal antibodies, Bruton tyrosine kinase inhbitors, phosphoinositide 3-kinase inhibitors, and B-cell lymyphoma-2 antagonists) improved the progression-free survival (PFS) compared with selected standard regimens in clinical trials for patients with relapsed/refractory chronic lymphocytic leukemia (CLL). Unfortunately, the relative efficacy of all possible therapeutic options remains unknown because there is no direct evidence for all possible comparisons. We aimed to compare the efficacy and safety of novel agents, chemotherapy, and immunotherapy using a Bayesian network meta-analysis (NMA). Systematic literature review with Bayesian NMA. An extensive systematic literature review of randomized clinical trials for relapsed/refractory CLL was performed. We searched for articles indexed in medical databases (MEDLINE, Embase, The Cochrane Library) and gray literature that could be further implemented into the Bayesian NMA. The systematic search identified 15 randomized trials that formed networks comparing PFS, overall survival (OS), overall response rates, and serious adverse events. Our study showed that all regimens containing novel agents significantly prolonged PFS compared with standard chemoimmunotherapy and immunotherapy. Among targeted drugs, venetoclax (VEN) + rituximab (RTX) had comparable efficacy in terms of PFS to zanubrutinib (ZAN) [hazard ratio (95% credible interval), 1.10 (0.59-2.08)], acalabrutinib (ACA) [0.78 (0.47-1.30)], ibrutinib (IBR) monotherapy [0.72 (0.41-1.27)], and other IBR-based regimens. ZAN was superior to IBR monotherapy [0.65 (0.49-0.86)] but not to ACA [0.71 (0.49-1.02)]. There were no significant differences in OS in any of the above comparisons. All novel therapies have better efficacy than chemoimmunotherapy and immunotherapy regimens. Among novel agents, the relative efficacy of VEN + RTX was similar to all BTKi, while ZAN was superior to IBR and comparable to ACA. PROSPERO CRD42022304330.

Ibrutinib versus bendamustine plus rituximab for first-line treatment of 65 or older patients with untreated chronic lymphocytic leukemia without del(17p)/TP53 mutation in China: a lifetime economic research study

BackgroundThe incidence and mortality rates of patients with chronic lymphocytic leukemia (CLL) in China have recently increased. This study performed a long-term economic evaluation of the first-line treatment strategies ibrutinib (IB) or bendamustine (BE) plus rituximab (RI) for previously untreated older patients with CLL without the del(17p)/TP53 mutation in China.MethodsBased on clinical data from large, randomized trials, a Markov model including four disease states (event-free survival, treatment failure, post-treatment failure, and death) was used to estimate the incremental costs per quality adjusted-life year (QALY) gained from the first-line IB strategy versus the BE plus RI strategy over a 10-year period. All costs were adjusted to 2022 values based on the Chinese Consumer Price Index, and all costs and health outcomes were discounted at an annual rate of 5%. Sensitivity analysis was performed to confirm the robustness of base-case results.ResultsCompared to the first-line BE plus RI strategy, first-line IB treatment achieved 1.17 additional QALYs, but was accompanied by $88,046.78 (estimated in 2022 US dollars) in decremental costs per patient over 10 years. Thus, first-line treatment with IB appeared to have absolute dominance compared to the BE plus RI strategy. Sensitivity analysis confirmed the robustness of these results.ConclusionsThe first-line treatment with IB is absolutely cost-effective compared to the first-line BE plus RI treatment strategy for 65 or older patients with CLL without the del (17p)/TP53 mutation from the Chinese payer perspective. Therefore, it is strongly recommended that Chinese health authorities select the former strategy for these CLL patients.

Studies on Fixed Dose Combination of Ibrutinib and Quercetin Self-Nanoemulsifying Drug Delivery Systems in Human Cancer Cell Lines

Ibrutinib (IB), irreversibly inhibits Bruton’s tyrosine kinase which plays a crucial role in the tumor microenvironment and quercetin (QC) has shown apoptosis induction, angiogenesis inhibition, and anti-proliferative action against several human carcinoma cells. The self-nano-emulsifying drug delivery system (SNEDDS) is suitable for loading insolubilized oil-based compounds such as ibrutinib and quercetin. In the current study IB with QC was formulated into SNEDDS and cytotoxicity was determined by using human malignant melanoma (A-375) and human lung adenocarcinoma (A549) cell lines. The optimized loaded formula consisted of castor oil, Kolliphor® RH 40, and PEG-600. The optimized formulation was evaluated for physical parameters and the results were satisfactory. For cytotoxicity studies MTT assay was conducted for these combinations, IC50 values were calculated for the tested compound. In A-549 adenocarcinoma cell line, the calculated IC50 values (μM) for the test compounds T1 (pure IB ± QC) and T2 (IB ± QC SNEDDS) were 70.34 ± 0.8 and 85.46 ± 0.93 μM at 24 hours study, respectively. In A-375 cancer cell line, IC50 values for the compounds T1 and T2 were 59.52 ± 0.87 and 88.43 ± 1.03 μM for 24 hours study, respectively. It was observed that the IC50 of IB-QC loaded SNEDDS was higher than pure drug combination and these enter the cells by active transport and induce cytotoxicity to the cells. The overall results from the studies suggest that IB-QC-loaded SNEDD provided synergistic effects, which could play a significant role in the percentage of cell death.

CD49d Expression Is Included in a Revised 4-Factor Model Predicting Outcome in Patients with Chronic Lymphocytic Leukemia Treated with Ibrutinib: A Multi-Center Real-World Experience

Introduction. Expression of the CD49d integrin chain has prognostic impact on ibrutinib (IB)-treated CLL patients (Tissino et al, J Exp Med, 2018; Tissino et al, Blood 2020). In addition, a 4-factor (4-f) score, based on TP53 aberration, β2-microglobulin (β2M), lactate dehydrogenase (LDH) and previous therapy lines was proposed to identify patients at a higher risk of treatment failure or death during IB therapy (Ahn et al, J Clin Oncol, 2020; Morabito et al, Am J Hematol, 2021). The clinical impact of TP53 disruption was recently refined by demonstrating that only the co-presence of TP53 deletion and mutations, and not the single aberrations, has prognostic value in the IB setting (Bomben et al, Leukemia 2022). The aim here is to integrate these observations in a comprehensive scoring for the management of IB-treated patients. Methods. This study is a retrospective/multicenter analysis of 410 CLL patients treated with IB in the current clinical practice (December/2013-March/2021). Outcome data were updated as of March/2023. Median follow-up from IB treatment was 29.5 months (95% CI 26.7-33.1 months); 57 patients were treatment naïve (0 previous lines), while 353 had ≥1 previous lines. CLL patients were characterized for CD49d expression and for the 4-f variables, TP53 disruption was evaluated by FISH and TP53 mutational status by NGS (low-VAF mutations included). OS or PFS were measured from the date of IB treatment to the date of death (OS), or progression/death (PFS) or last follow-up. Results. 1) The canonical 4-f was applied as previously described, identifying 111 low-, 163 intermediate (int)-, and 136 high-risk patients. Patients in the low-risk group had a longer OS than patients in the int-, and high-risk groups ( P=0.0115 and P=0.0011), while no difference was found comparing patients in the int- vs. high-risk groups (P=0.3036). 2) We generated a modified version of the 4-f score by considering: i) as TP53 disrupted only patients presenting a concomitant TP53 deletion and mutation (n=93); ii) since no difference in terms of OS was found comparing previously untreated patients (n=57) and patients treated with 1 previous line (n=157; P=0.78), these two groups were combined (n=214) and kept separated from patients who had received >1 previous lines of therapy (n=196). Accordingly, the 4-f-modified identified 218 low-, 109 int-, and 83 high-risk patients, the 3 groups presented different OS, the latter model outperforming the canonical 4-f score (C-indices 0.616 vs 0.639; P<0.0001). 3) CD49d-high CLL cases (i.e. CLL with CD49d expression ≥30% and/or with CD49d-bimodal expression; n=268) had shorter OS and PFS intervals ( P=0.0005 and 0.0194, respectively) than CD49d-low cases (n=142). By combining these observations, CD49d remained an independent prognostic factor for OS ( P=0.004) in a multivariable model, which included the 4-f-modified int-risk ( P=0.0585) and high-risk ( P=0.0011) groups. Driven by these findings, we re-analyzed the single parameters of the 4-f score along with CD49d expression. According to a new multivariable analysis (Fig. A), LDH was not included in the final model, which in turn included CD49d expression as independent OS predictor ( P=0.0011). 4) We then redesigned a novel 4-f model excluding LDH data in favor of CD49d expression data (4-factor-CD49d). Each of the four factors contributed one point and stratified patients (n=407/410) into three groups with a significantly different risk for OS probability, merged on a one-to-one risk group comparison basis: score 0-1, low-risk (n=185); score 2-3, int-risk (n=211); score 4, high-risk (n=11; Fig. B). The inclusion of CD49d into this novel 4-f model improved its prediction capability (C-index=0.663; P<0.0001 versus both the original 4-f and the 4-f-modified). Similar results were obtained when considering PFS as clinical readout. Conclusions. Evidence is provided that in the context of CLL patients treated with IB in a real-world setting, variables like B2M, the number of previous lines of therapy and assessment of TP53 disruption remain important tools for identifying patients at a higher risk of relapse/death. Here we emphasize the need of a comprehensive assessment of TP53 aberrations considering TP53 deletions and mutations simultaneously, and propose to add the assessment CD49d expression, integrating these four variables into a novel 4-f-CD49d scoring system. Further validation in independent cohorts is needed.

Ibrutinib in Combination with Revlimid/Dexamethasone (Rd) in Relapsed/Refractory Multiple Myeloma (AFT-15)

Introduction: Preclinical studies have suggested synergism between lenalidomide (LEN) and ibrutinib (IBR) in multiple myeloma (MM). Both downregulate IRF4, a master transcriptional factor that regulates myeloma cell survival. Single agent oral IBR combined with dexamethasone proved well tolerated and active in advanced, steroid refractory relapsed MM as part of a large Phase1/2 study in 60 patients, with durable stabilization and minimal response seen in most evaluable patients (Richardson PG et al, BJH 2018). LEN is considered a standard of care in newly diagnosed MM, as maintenance and in relapsed disease, and a backbone of oral therapy in the MM treatment paradigm (Laubach JP et al, Leukemia 2016). Methods: We therefore conducted a 3+3 phase I trial to determine the maximum tolerated dose (MTD) of IBR in combination with LEN + dexamethasone (DEX) in patients with relapsed/refractory (RR) MM who had at least 2 prior lines of therapy. Three dose levels (DL) were planned. Cycle length was 28 days. IBR was administered orally daily at 560mg on DL1-2 and 840mg on DL3, LEN orally days 1-21 at 15mg on DL1 and 25mg on DL2-3, and DEX orally days 1, 8, 15, and 22 at 40 mg if age < 75 or 20 mg if ≥75 for DL1-3. Patients with GFR ≥ 30 and < 60 were treated according to manufacturer's instructions with lenalidomide dosed at 10mg/d. Dose limiting toxicities (DLT) included grade 4 thrombocytopenia; grade 4 neutropenia lasting more than 5 days or febrile neutropenia; grade 4 nausea, vomiting or diarrhea; grade 3 thrombocytopenia with bleeding or platelet transfusion; grade 3-4 hyperglycemia or thrombotic/embolic event, treatment delays ≥ 21 days for toxicity; and treatment related death. Due to changes in standard of care during the study, eligibility was modified to allow the enrollment of patients with RRMM who had at least 1 prior line of therapy. Response was assessed using IMWG/Uniform Criteria. Results: Fourteen patients (DL1-6 pts; DL2-3 pts; DL3-5 pts) registered to the study from March 2019 to May 2023, prior to its closure due to slow accrual. One patient on DL3 cancelled participation prior to start of treatment due to disease progression (PD). The remaining 13 patients are included in summary of toxicities and response but 2 patients on DL3 are excluded from determination of MTD due to discontinuing cycle 1 treatment due to COVID and receiving 280 mg/day of IBR instead of assigned 840 mg/day dose during cycle 1, respectfully. Twelve patients were evaluable for response. The median number of prior lines of therapy was 3 (range: 2-9), reflecting a heavily pretreated relapsed and refractory population. One of the 6 patient on DL1 developed a DLT, grade 3 non-viral hepatitis. None of the 3 patients on DL2 or the 2 patients on DL3 had a DLT. One patient on DL1 remains on treatment with stable disease for 42+ cycles. The median number of cycles administered was 3 (range: 1-42+). Severe toxicities reported included grade 3 lymphocytopenia (3), anemia (2), alanine aminotransferase increase (1), aspartate aminotransferase increase (1), blood bilirubin increase (1), hypocalcemia (1), hypokalemia (1) hypophosphatemia (1), febrile neutropenia (1), chronic kidney disease (1), non-viral hepatitis (1), soft tissue infection (1), and fatigue (1); grade 4 lymphocytopenia (1), and grade 5 sepsis (1). End of treatment reasons included: PD (7), toxicity (2), death [soft tissue infection that turned into sepsis considered to be likely related to DEX] (1), and concomitant conditions (2). Stable disease (SD) or better was achieved in 10 of 12 evaluable patients (83%), including one patient who achieved disease control for over 3.5 years. One patient (8%) on DL3 had a complete response (CR) but stopped treatment after 2 cycles due to reversible toxicity and comorbid conditions, based upon physician advice and patient choice. Conclusions: The combination of lenalidomide with Ibrutinib as an all-oral approach in RR MM proved feasible and generally tolerable, with the majority of discontinuation seen in this Phase I study due to disease progression. No COVID related - mortality was seen. SD or better was achieved in 83% of patients, including one CR. Potential future directions include combination approaches with next generation IMids such as pomalidomide, as well as other orally bioavailable novel agents with potent immune activating properties, such as CelMoDs. Support: AFT; Pharmacyclics; Clinicaltrials.gov Identifier: NCT03702725

Depletion of the Mitochondrial E3 Ligase MARCH5 Induces Synthetic Lethality to BCL2 Inhibitor (Venetoclax) Therapy in Cell Lines Representative of Diverse Blood Cancers

Combination therapies incorporating the BCL2 inhibitor, venetoclax (VEN), are standards of care in chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML), and display promising activity against mantle cell lymphoma (MCL), multiple myeloma (MM) and many other hematologic malignancies. However, primary resistance is observed in some diseases and even across responsive malignancies, enduring cells typically persist, ultimately driving relapse and precluding cure. Genome wide CRISPR/Cas9 screens have the potential to identify novel mediators of venetoclax resistance. However, conventional knock-out/drop out (KO/DO) screens have several limitations including the frequent identification of common essential genes as false positives and the large scale required to detect DO with high statistical confidence. We devised a novel augmentation on the conventional CRISPR/Cas9 KO/DO screen utilizing two MCL cell lines (Jeko1, Z138) which were both resistant to apoptosis induced by VEN +/- ibrutinib (IBR)(Fig 1). Rather than detecting sensitizing hits through DO, we positively enriched for sensitizing hits by flow-sorting the rare (~10%) population of cells initiating apoptosis as indicated by AnnexinV positivity after brief (6hr) BH3-mimetic exposure. At this early time point, cells whose KO had led to a lowered apoptotic threshold could be identified without sufficient time for DNA degradation. DNA yield from dying cells approached 100% efficiency. sgRNA frequencies among the control cells and those undergoing early apoptosis were analyzed using MAGecKE-MLE. This method was anticipated to reduce common essential gene contamination, increase statistical power to detect sensitizing hits due to enrichment rather than DO of relevant genes, and identify targets likely to exhibit synthetic lethality (i.e. neither VEN nor KO alone are lethal, but combination achieves potent killing). The screens in both cell lines demonstrated significant depletion of common essential genes defined by DepMap by D14 (prior to treatment). Consistent with the increased power expected from a positive selection screen, both yielded >50 statistically significant VEN-sensitizing hits, after correction for multiple hypothesis testing. These included the expected KOs of MCL1 and BCL2L1 (BCL-X L), confirming the validity of the method. sgRNAs resulting in KO of the E3 ligase MARCH5 were among the most enriched within dying (VEN-sensitized) cells in both Jeko1 and Z138 screens, with either VEN only or VEN+IBR treatment (Fig 1). The screen method was repeated in Jeko1 cells using the MCL1 inhibitor AMG176 and BCL-X L inhibitor A1331853, and again yielded BCL2 as well as novel hits, including MARCH5 KO as a sensitizing hit to BCL-X L inhibition. KO of MARCH5 markedly sensitized multiple human blood cancer cell lines to venetoclax (Table 1), including sensitive and resistant lines, with and without functional TP53. In Jeko1 (MCL) cells, which are highly resistant to BCL2 or BCL-X L inhibition when wildtype (10-20% apoptosis at 6µM), MARCH5 KO induced marked sensitization to single-agent VEN (LC50 8nM) or A1331853 (LC50 375nM).By introducing a degron dTAG MARCH5 construct into MARCH5 KO Jeko1 cells, we demonstrated dose-dependent sensitisation to VEN with MARCH5 depletion, marked synergy (mean Bliss score: 22.97) and synthetic lethality. Degron dTAG-mediated depletion of MARCH5 demonstrated synergy with venetoclax in MOLM13 (AML) and Z138 (MCL) cell lines, and enhanced in vitro killing of MOLM13 by VEN + azacytidine, and killing of Jeko1 and Z138 by VEN + IBR. CRISPR “death” represents a powerful modification to conventional CRISPR KO screens, with reduced common essential gene false positives, increased statistical power and enrichment for synthetic lethal hits. We demonstrate the pan-hematologic, dose-dependent VEN-sensitization achieved by MARCH5 depletion across multiple blood cancer lines with and without normal TP53 function. MARCH5 depletion also sensitizes blood cancer cell lines to BCL-X L inhibition. Addition of MARCH5 depletion to VEN-combination treatment improved MCL and AML killing in vitro and this target should be prioritized for accelerated drug development.

Combined Ibrutinib and Venetoclax for First-Line Treatment of Patients with Chronic Lymphocytic Leukemia (CLL): 5-Year Follow-up Data

Background: Ibrutinib (IBR) and venetoclax (VEN) combination is an effective therapy for patients (pts) with CLL. We previously reported results of the first-line cohort of a phase II trial of combined IBR and VEN for high-risk pts with CLL (Jain, NEJM 2019, JAMA Oncology 2021). Here we report updated data for 120 pts (80 pts in the original published cohort and 40 pts in an expansion cohort) with a median follow-up of 61.5 months. Methods: Pts with previously untreated CLL meeting IWCLL treatment criteria were enrolled. All pts had at least one high-risk feature: del(17p), mutated TP53, del(11q), unmutated IGHV, or age ≥65 years. Pts received IBR 420 mg daily for 3 cycles followed by addition of VEN (weekly dose-escalation to 400mg daily). Combined therapy was given for 24 cycles (28 days/cycle). Pts with bone marrow (BM) undetectable MRD (U-MRD) (flow cytometry; sensitivity 10 -4) at 24 cycles of combined therapy discontinued both VEN and IBR; MRD+ pts continued IBR. A trial amendment allowed an additional 12 cycles of combined VEN and IBR for pts who remained BM MRD+ after Cycle 24. Response assessments included BM and CT studies (2008 IWCLL criteria). U-MRD was defined as <0.01%; low MRD+ 0.01% to <1%; high MRD+ ≥1%. Progression-free survival (PFS) was assessed as the time from the start of study drug to CLL progression, Richter transformation, or death from any cause. Blood MRD was monitored every 6 months after active therapy. Results: Between August 2016 and February 2019, a total of 120 pts were enrolled. Median age was 64.5 years (range, 26-88 years). 86% had IGHV-unmutated CLL. 23% had del(17p)/ TP53 mutation. The median follow-up is 61.5 months. Six pts came off study during 1 st 3 cycles of IBR monotherapy; 114 pts initiated VEN. After 12 cycles of the combination, 62/120 (52%) achieved BM U-MRD remission; 43/120 (36%) were BM MRD-positive (low MRD+, n=35; high MRD+, n=8). After 24 cycles of the combination, 77/120 (64%) achieved BM U-MRD remission; 24/120 (20%) were BM MRD+ (low MRD+, n=23; high MRD+, n=1). Overall, 86/120 (72%) achieved BM U-MRD as the best response. One pt had DLBCL transformation and 1 pt had CLL progression during the first 2 year of therapy (details below). The 5-year PFS is 90.1% and 5-year OS is 95.6% (Figure 1). The 5-year PFS for pts with del(17p)/ TP53 mutation (n=27) is 86.1%. Of the 77 pts who were BM U-MRD at the end of cycle 24 of the combination, 73 discontinued all therapy, 4 pts continued IBR per treating physician discretion. Among these 77 pts, with a median follow-up of 40 months post Cycle 24, 22 pts had recurrence of blood MRD (defined as MRD ≥0.01% in 2 consecutive visits). Of the 22 pts with MRD recurrence, 5 pt had CLL progression at a median of 18 months (range, 6-30 months) from MRD recurrence (details below); 16 are being monitored without any active therapy for CLL and without clinical disease progression; 1 pt died from mesothelioma. Among the 55 pts who remain in blood U-MRD remission, 53 remain in long-term follow-up in U-MRD remission; 1 pt had B-PLL transformation and 1 patient died (found unresponsive at home; was off therapy for 2 years). There were 24 pts who were BM MRD+ at the end of cycle 24 of the combination (low MRD+, n=23; high MRD+, n=1). The only pt with high-MRD+ at end of cycle 24 was noted to have Richter transformation at that time. The remaining 23 pts (all low MRD+ in BM, range 0.01-0.95%) continued IBR monotherapy. With a trial amendment, MRD+ pts after Cycle 24 could get 12 additional cycles of VEN; 18/23 pts have resumed VEN. 11/18 (61%) pts achieved U-MRD remission during the third year of combined therapy. Only 2/23 pts are still receiving IBR (remaining pts have d/c IBR; all pts have d/c venetoclax); none of these 23 pts had clinical relapse. A total of 6 pts had CLL progression (1 during the first 2 yr of therapy; remaining 5 during off-therapy phase). 3/6 had evaluation of BTK, PLGG2 and BCL2 mutations at the time of relapse and none were detected. 5 pts have started subsequent therapy (acalabrutinib, n=4; ibrutinib, n=1; all are clinically responding); 1 pt has not yet started therapy. Conclusions: We report long term follow-up of combined IBR and VEN in first-line CLL (n=120) with a 5-year PFS of 90.1%. The 5-year PFS for pts with del(17p)/ TP53 mutation is 86.1%. Retreatment with BTK inhibitor appears effective for pts with disease relapse.

Reappearance of CXCR4 dim/CD5 bright Proliferative Fraction Associates with BTK Mutations and Anticipates Progression in Ibrutinib-Treated CLL

Reciprocal expression of CXCR4 and CD5 on the surface of chronic lymphocytic leukemia (CLL) cells can discriminate the proliferative fraction (CD5high/CXCR4dim, PF), recently egressed from the lymph node, from the resting fraction (CXCR4high/CD5dim, RF) of older, quiescent cells. BTK inhibitors affect the proliferative capacity of CLL cells and cause the redistribution from nodal compartments to the blood stream. Nevertheless, little is known about the impact of long-term treatment of the BTK-inhibitor ibrutinib (IBR) on the PF/RF phenotype. Here, we monitored the PF dynamics in two cohorts of IBR-treated CLL cases with long-term follow-up, and correlated with the emergence of IBR resistance. Longitudinal analysis of the PF under IBR in 31 CLL cases, enrolled in the IOSI-EMA-001 with sequential blood samplings (156 samples, median 6 samples/case) showed a depletion of the PF over time, from 17.7% at pre-treatment to 4.75, 0.4, 1.5, 0.6, 1.5% at later timepoints (0.5, 6, 12, 18, 24 months; p < 0.001, U test), along with loss of proliferative potential by Ki67 expression. We then retrospectively analyzed the PF in 100 IBR-treated CLL cases from the real world, referred for routine immunophenotyping (296 samples, median 3 samples/case). Median PF of pre-IBR samples was 12.0% (range 0.7-50), with a significant drop to 2.7% within one year of treatment and to 1.0% in the second year (p<0.001, U test). 77 cases discontinued IBR due to: toxicity (n=13), progression (n=51), other/death (n=13). Mutations of BTK/ PLCG2 were detected in 30 cases, 28 of which discontinued IBR due to progression and 2 for other/death. To correlate reappearance of the PF with cause of discontinuation, we focused on 64 cases collected within 12 months before/after IBR discontinuation due to toxicity (n=10), progression (n=47) or other/death (n=7), and compared with 22 samples still on treatment for the next 12 months after testing (Panel A). ROC analysis of the PF suggested a criterion of PF>3% as the most discriminating to predict IBR discontinuation due to progression, with a sensitivity of 86.7% and a specificity of 71.1%. This cut-off could separate patients with a longer time-to-progression (median 56 vs. 45 months, p=0.031). 26/47 progressing cases bore BTK/ PLCG2 mutations, with a PF higher than wild-type cases discontinuing for toxicity (8.4% vs. 2.2%; p<0.001) or still on treatment (1.8%, p<0.001). Notably, the 21 BTK/ PLCG2- wild-type progressing cases also showed higher PF compared to cases discontinuing for toxicity (6.9% vs. 2.2%; p<0.001) or still on treatment (1.8%; p<0.001). Notably, PF levels showed no significant correlation with white blood cell counts. Sequential dosages of plasmatic B2M in progressing cases (n=5) revealed steady levels below the 3.5 ug/mL threshold, despite the PF increase (median PF 18%). Cell sorting of the PF/RF fractions from 10 cases showing PF reappearance after prolonged IBR treatment (median 50.7 months) revealed a mean of 1.7 BTK mutations per sample (27 total, range 1-4), a median VAF higher in the PF (23.0%, 0.3-92.3) on average 2.8 times larger than in the RF (5.2%, 0.1-84.8; p=0.003, paired rank test). A similar skewing was present for PLCG2 mutations (median PF VAF: 2.0%, 0.1-6.2; RF VAF: 1.35%, 0.4-2.8; p=0.014). Finally, mRNA-seq was performed in 20 cases, on matching PF/RF fractions both at pre-IBR and progression (9 cases with BTK mutations). Differential expression signature of pre-IBR PF vs. RF, concordant with published gene sets, drove co-clustering of post-IBR PF/RF with their respective counterparts, indicating that PF at progression functionally resembles its pre-treatment counterpart. A strong enrichment of multiple proliferation-related signatures, present in pre-treatment samples, was significantly up-regulated also at progression, independently from BTK mutations (Panel B). In summary, here we report that CLL progression under IBR associates with reappearance of the CD5bright/CXCR4dim PF which precedes clinical progression, increase of serum B2M and WBC counts. Transcriptomic/genetic profiling of the post-IBR PF suggests presence of clonal selection dynamics and active bypass signaling pathways, bona fide taking place within the lymph node microenvironment, including BTK/ PLCG2 mutations. Clinically, longitudinal monitoring of the CXCR4/CD5 fractions by flow cytometry may provide a simple tool helping to intercept CLL progression under IBR therapy.

NIR-Actuated Targeted Janus Nanomotors Remodel Immunosuppressive Tumor Microenvironment for Augmented Cancer Immunotherapy.

Tumor-associated macrophages (TAMs) always display immunosuppressive M2 phenotype in the tumor microenvironment to facilitate tumor growth, invasion, and metastasis. Ibrutinib (IBR), a novel irreversible Bruton's tyrosine kinase (BTK) inhibitor, has been employed to repolarize the BTK-overexpressed TAMs from M2 to M1 phenotype to remodel the immunosuppressive tumor microenvironment. However, the poor solubility of IBR extremely hinders its bioavailability, which results in low tumor accumulation and TAMs uptake in vivo. Herein, NIR laser-actuated Janus nanomotors are proposed for the effective and deep delivery of IBR to TAMs in solid tumor for targeted immunotherapy. Under NIR irradiation, the Janus nanomotors exhibit efficient photothermal conversion to produce powerful propulsion via self-thermophoresis with a speed of 12.15µm s-1 . Combined with the salic acid targeting and IBR loading, the nanomotors significantly boost their binding and uptake efficacy by M2-like macrophages during the active motion, which highly facilitate the reprogramming of M2 to M1 macrophages in vitro. Furtherly, the autonomous motion also validly improves in vivo accumulation and penetration depth in tumors to alter the M1/M2 polarization balance and activate T cells. Overall, the synthesized IC@MSA JNMs would provide a promising strategy for the efficient delivery of immunological agents toward targeted cancer immunotherapy.

In Silico Screening as a Tool to Prepare Drug-Drug Cocrystals of Ibrutinib-Ketoconazole: a Strategy to Enhance Their Solubility Profiles and Oral Bioavailability

Ibrutinib (IBR) is a biopharmaceutical classification system (BCS) class II drug and an irreversible Bruton’s tyrosine kinase (BTK) inhibitor. IBR has an extremely low oral bioavailability due to the activity of the CYP3A4 enzyme. The current intention of the research was to enhance solubility followed by oral bioavailability of IBR using the hot melt extrusion (HME) technique by formulating drug-drug cocrystals (DDCs). Ketoconazole (KET) is an active CYP3A4 inhibitor and was selected based on computational studies and solubility parameter prediction. Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), proton nuclear magnetic resonance (1H NMR), and scanning electron microscopy (SEM) evaluations were employed for estimating the formation of IBR-KET DDCs. The IBR-KET DDC system was discovered to have a hydrogen bond (H-bond) and π-π-stacking interactions, in accordance with the computational results. Further, IBR-KET DDCs showed enhanced solubility, stability, powder dissolution, in vitro release, and flow properties. Furthermore, IBR-KET-DDCs were associated with enhanced cytotoxic activity in K562-CCL-243 cancer cell lines when compared with IBR and KET alone. In vivo pharmacokinetic studies have shown an enhanced oral bioavailability of up to 4.30 folds of IBR and 2.31 folds of KET through IBR-KET-DDCs compared to that of the IBR and KET suspension alone. Thus, the prepared IBR-KET-DDCs using the HME technique stand as a favorable drug delivery system that augments the solubility and oral bioavailability of IBR along with KET.Graphical abstract

Quality by design endorsed fabrication of Ibrutinib-loaded human serum albumin nanoparticles for the management of leukemia

Ibrutinib (IB), a BCS class II drug suffers from limited aqueous solubility, short half-life and extensive first-pass metabolism. In this project, we aim to recruit the desirable properties of human serum albumin (HSA) as a biocompatible drug carrier to circumvent nanoparticle-associated drawbacks. Quality by design and multivariate analysis was used for the optimization of IB-NPs. Cell culture studies performed on the K562 cell line revealed that the Ibrutinib-loaded HSA NPs demonstrated improved cytotoxicity, drug uptake, and reactive oxygen species generation in the leukemic K562 cells. Cell cycle analysis revealed G2/M phase retention of the leukemia cells. In vitro protein corona and hemolysis studies revealed superior hematological stability compared to the free drug which showed greater than 40 % hemolysis. In vitro drug release studies showed prolonged release profile till 48 h. Pharmacokinetic studies demonstrated a 2.31-fold increase in AUC and an increase in half-life from 0.43 h to 2.887 h with a tremendous reduction in clearance and elimination rate indicating prolonged systemic circulation which is desirable in leukemia. Hence, we conclude that IB-loaded albumin nanoparticles could be a promising approach for the management of leukemia.

Core Shell Lipid-Polymer Hybrid Nanoparticles for Oral Bioavailability Enhancement of Ibrutinib via Lymphatic Uptake.

The purpose of thisresearch was to develop ibrutinib (IBR)-loaded lipid-polymer hybrid nanoparticles (IBR-LPHNPs) to improve oral absorption by intestinal lymphatic uptake. IBR-LPHNPs were fabricated by nanoprecipitation method using poly(lactic-co-glycolic acid), lipoid S 100, and DSPE-MPEG 2000. The IBR-LPHNPs showed particle size of 85.27±3.82 nm, entrapment efficiency of 97.70±3.85%, and zeta potential of -24.9±3.08 mV respectively. Fourier transform infrared spectroscopy and differential scanning calorimetry study revealed compatibility between IBR and excipients. X-ray diffraction study showed the conversion of IBR into amorphous form. High-resolution transmission electron microscopic image displayed spherical-shaped, discrete layered polymeric core and lipid shell structure. The drug release from IBR-LPHNPs exhibited prolong release profile up to 48 h and was best fitted to Korsmeyer-Peppas model. Higher fluorescence intensity at the end of 2 h in the intestinal tissue confirmed the uptake of LPHNPs by Peyer's patches. The oral bioavailability of IBR was improved 22.52-fold with LPHNPs as compared to free IBR. The intestinal lymphatic uptake study in rats pretreated with cycloheximide confirmed the intestinal lymphatic uptake of IBR-LPHNPs. All the results conclusively showed that LPHNPs could be a promising approach to improve oral bioavailability of IBR.

5‐YEAR (Y) FOLLOW‐UP OF A PHASE 2 STUDY OF IBRUTINIB PLUS FLUDARABINE, CYCLOPHOSPHAMIDE, RITUXIMAB (IFCR) AS INITIAL THERAPY FOR YOUNGER CLL PATIENTS (PTS)

Introduction: This frontline study investigates whether iFCR followed by 2Y ibrutinib (IBR) maintenance (I-M) could provide deep and durable responses in CLL irrespective of IGHV status. We previously reported high rates of bone marrow undetectable minimal residual disease (BM-uMRD) in both IGHV unmutated (U-IGHV, 83%) and mutated (M-IGHV, 82%) pts (Davids et al., Lancet Haematol, 2019). Here, we report updated data at a median follow-up of 63 months. Methods: In this phase 2 investigator-sponsored trial (NCT02251548), eligible pts received up to 6 cycles of iFCR followed by 2Y I-M. Pts with BM-uMRD after 2Y I-M had the option to stop IBR. MRD was assessed with multicolor flow at 10-4. Targeted NGS covering 97 genes was applied to peripheral blood (PB) samples at MRD recurrence. Results: 85 pts with a median age of 55Y (range 38–65) were treated, including 53% with U-IGHV and 6% with del17p and/or TP53MUT. 77 pts (91%) completed 2Y I-M. 20 pts continued IBR beyond 2Y I-M, including 13 with detectable MRD in BM or PB at 2Y. Safety was similar to our previous report; the cumulative incidence of atrial fibrillation was 8%, and second malignancy occurred in 11%, mostly non-melanoma skin cancer. Two pts (2%) had secondary myeloid neoplasms. No new deaths have occurred since the one death reported in the prior publication (sudden cardiac death during I-M). 5Y PFS was 94% (95% CI 89%–100%) and 5Y OS was 99% (95% CI 96%–100%). There was no difference in PFS by IGHV status or duration of I-M (Figure A). Five pts progressed with CLL, all after cessation of IBR. Fourteen pts remained in response on continuous IBR therapy, two of whom had achieved BM-uMRD at 2Y but chose to continue IBR. We longitudinally tracked PB MRD of 69 pts treated with at least 2Y of I-M with available samples and observed high rates of PB-uMRD post-iFCR (75%) and after 2Y I-M (77%). At 4Y after completion of iFCR, 63% of evaluable pts maintained PB-uMRD (Figure B). Thirteen pts (15%) had MRD recurrence without clinical progression, mostly after stopping IBR; 62% of these pts had U-IGHV, 7% del17p, and 15% NOTCH1MUT. BTKMUT was not detected in any of the ten pts analyzed at time of MRD recurrence. One pt had PLCG2MUT at a low allele frequency (2%). Driver gene mutations were commonly detected at MRD recurrence (23% with TP53MUT, 38% with 1–2 other mutations per pt affecting NOTCH1, SF3B1, ATM, XPO1, and/or BRAF). Four of six pts (67%) who received IBR retreatment after MRD recurrence achieved PR. Median duration of IBR retreatment was 34 months. Serial PB MRD data from five pts on IBR retreatment revealed that the MRD growth stabilized but was not eradicated during retreatment. Keywords: chronic lymphocytic leukemia (CLL), minimal residual disease, molecular targeted therapies This study was funded by Pharmacyclics, an AbbVie Company. Conflicts of interests pertinent to the abstract I. E. Ahn Consultant or advisory role: BeiGene D. M. Brander Conflicts of interests pertinent to the abstract Consultant or advisory role: Pfizer, Pharmacyclics, Genentech, TG Therapeutics, ArQule/Merck, AbbVie Research funding: Juno/Celgene/BMS, AstraZeneca/Acerta, CATO/SMS Catapult, NeWave, DTRM, Genentech, BeiGene, MEI Pharma, ArQule/Merck, AbbVie Other remuneration: Ascentage J. Montegaard Consultant or advisory role: Pharmacyclics, Abbvie, AstraZeneca A. Alencar Consultant or advisory role: Amgen, Kite, Seagen, Epizyme, Janssen, BeiGene, Incyte, TG Therapeutics, Genentech, Lilly Research funding: Loxo, BeiGene, Incyte C. A. Jacobson Consultant or advisory role: Kite/Gilead, BMS/Celgene, Novartis, Miltenyi, Abintus Bio, Ipsen, Instil Bio, Daiichi-Sankyo, Morphosys, Caribou Bio, ImmPACT Bio, AztraZeneca Research funding: Kite/Gilead, Pfizer P. Armand Consultant or advisory role: Merck, BMS, Pfizer, Affimed, Adaptive, Infinity, ADC Therapeutics, Celgene, Morphosys, Daiichi Sankyo, Miltenyi, Tessa, GenMab, C4, Enterome, Regeneron, Epizyme, Astra Zeneca, Genentech, Xencor Honoraria: Merck, BMS Research funding: Kite; Research funding (institutional), Merck, BMS, Affimed, Adaptive, Tensha, Otsuka, Sigma Tau, Genentech/Roche, IGM J. Crombie Consultant or advisory role: Incyte, Karyopharm, Kite, ADC therapeutics, Genmab Research funding: Roche, Merck, Abbvie, Bayer A. S. LaCasce Consultant or advisory role: Seagen, Kite Honoraria: Research to practice J. Arnason Consultant or advisory role: BMS E. P. Hochberg Other remuneration: Leuko (Equity) J. S. Abramson Consultant or advisory role: Abbvie, Astra-Zeneca, BeiGene, Bluebird Bio, BMS, Celgene, Epizyme, Incyte, Kymera, Genmab, Genentech, Ono Pharma, Mustang Bio, MorphoSys, Regeneron, Century, Kite Pharma, Lilly, Janssen, Takeda, Caribou Biosciences, Interius, Cellectar J. R. Brown Consultant or advisory role: Abbvie, Acerta/Astra-Zeneca, BeiGene, Genentech/Roche, Grifols Worldwide Operations, Hutchmed, iOnctura, Janssen, Kite, Loxo/Lilly, MEI Pharma, Numab Therapeutics, Pfizer, Pharmacyclics Research funding: BeiGene, Gilead, iOnctura, Loxo/Lilly, MEI Pharma, TG Therapeutics M. S. Davids Consultant or advisory role: AbbVie, Adaptive Biosciences, Ascentage Pharma, AstraZeneca, BeiGene, BMS, Eli Lilly, Genentech, Janssen, Merck, Mingsight Pharmaceuticals, ONO Pharmaceuticals, Secura Bio, TG Therapeutics, Takeda Research funding: AbbVie, AstraZeneca, Ascentage Pharma, Genentech, MEI Pharma, Novartis, Surface Oncology, TG Therapeutics

Matching-adjusted indirect comparison (MAIC) of zanubrutinib (ZANU) versus ibrutinib (IBRU) in relapsed/refractory marginal zone lymphoma (R/R MZL).

e19527 Background: ZANU is a Bruton tyrosine kinase inhibitor (BTKi) that has been evaluated for the treatment of R/R MZL in two phase 2, single-arm trials (MAGNOLIA, n=66, NCT03846427; BGB-3111-AU-003, n=20, NCT02343120). At 28 and 35 months of study follow-up in MAGNOLIA and BGB-3111-AU-003, respectively, median progression-free survival (PFS) and overall survival (OS) were not reached. IBRU, a first-generation BTKi, has also been evaluated for R/R MZL in a phase 2, single-arm trial (PCYC-1121, n=60 [Noy et al., Blood 2017; Noy et al., Blood Adv 2020]). Here, we conducted an unanchored MAIC to estimate the comparative efficacy of ZANU vs IBRU in R/R MZL. Methods: The MAIC utilized study-level data from PCYC-1121 and pooled individual patient-level data from MAGNOLIA and BGB-3111-AU-003. A logistic propensity score model was used to estimate weights for patients in the ZANU trials so that weighted mean baseline characteristics matched those in PCYC-1121. The following characteristics were identified as key prognostic factors and included in the base case propensity score model: number of prior lines of therapy, MZL subtype, response to prior therapy, and age. A sensitivity analysis was conducted including additional characteristics (B symptoms, time since last therapy, prior anti-CD20 therapy, bulky disease [>5cm], and lactate dehydrogenase above normal). Comparisons were conducted for OS, PFS, and objective response rate (ORR) by independent review committee using weighted statistical models with relative treatment effects presented as hazard ratios (HRs), odds ratios (ORs), and 95% CIs. Results: After applying weights estimated from the base case propensity score model, the effective sample size (ESS) for ZANU was 68 (Table). Compared with IBRU, ZANU reduced the risk of progression (HR 0.38; 95% CI 0.21–0.69) and was associated with a higher ORR (OR 2.37; 95% CI: 1.13–4.96). OS was comparable for ZANU and IBRU, which is consistent with expectations for indolent lymphomas. The sensitivity analysis accounting for additional prognostic factors suggested the two treatments were comparable across all outcomes, owing in part to the low ESS (24) for ZANU associated with the expanded model. A leave-one-out analysis showed improved PFS (HR 0.33–0.45) for ZANU when excluding B symptoms, time since last therapy, or bulky disease from the expanded model. Conclusions: This MAIC demonstrated ORR and PFS benefits for ZANU vs IBRU in R/R MZL. [Table: see text]

Real-world treatment outcomes in patients with chronic lymphocytic leukemia or small lymphocytic lymphoma who were treated with first-line single-agent ibrutinib vs. chemoimmunotherapy.

e19509 Background: Real-world evidence on Bruton Tyrosine Kinase Inhibitor treatment vs chemoimmunotherapy (CIT) for patients with chronic lymphocytic leukemia or small lymphocytic lymphoma (CLL/SLL) has been limited to certain practice settings; research using a large and more comprehensive data source is warranted. Methods: This retrospective cohort study evaluated treatment outcomes among patients with CLL/SLL treated with first-line (1L) ibrutinib (IBR) or CIT using the US claims data from the Komodo Health payer-complete dataset, derived from >150 private insurers and >140 million insured individuals from 2015 to 2022. This study included adult patients with CLL/SLL who initiated 1L single-agent IBR or CIT (defined as no prior CLL/SLL treatment for ≥12 months in the baseline period) on or after March 2016. Time to next treatment (TTNT) was defined as the time from initiation (index date) of 1L treatment to treatment add-on or switch to a next line of therapy ≥29 days post-index and was compared using Cox proportional hazards models. Cohorts were balanced on baseline characteristics using inverse probability of treatment weights. Results: A total of 3570 1L IBR- and 2391 CIT-treated patients were included, with the mean age 68 vs 64 years, 63% vs 66% male, and mean Quan-Charlson Comorbidity Index score 2.87 vs 3.05, respectively. Median follow-up was 26 vs 31 months, and 13% vs 26% of patients recorded a next treatment during the study period for IBR and CIT, respectively. At 1-, 3-, and 5-year post-index, the probabilities (95% confidence interval [CI]) of not initiating a new treatment were 92% (91%-93%), 83% (81%-84%) and 76% (73%-78%) vs 88% (87%-89%), 70% (68%-73%) and 56% (53%-60%) for the IBR and CIT cohorts, respectively. After controlling for baseline characteristics, 1L IBR patients were significantly less likely to initiate the next line of therapy during the study period (hazard ratio 0.61, 95% CI 0.54-0.69, p<0.001). Conclusions: 1L single-agent IBR was associated with a significantly lower risk of advancing to next line of treatment compared to CIT in this large claims-based data set, reinforcing real-world effectiveness of 1L IBR for CLL in an insured US patient population. [Table: see text]