Combination Therapy Of Ibrutinib Research Articles

Efficacy and Safety of Ibrutinib as Monotherapy or Combination Therapy in Relapsed/Refractory Diffuse Large B-cell Lymphoma (R/R DLBCL): A Systematic Review and Meta-analysis.

Diffuse large B-cell lymphoma (DLBCL) is a highly heterogeneous disease group. Ibrutinib's monotherapy or combination therapy is effective in relapsed/refractory (R/R) DLBCL. However, the treatment response in R/R DLBCL varies from 15% to 90% with different regimens, and the tolerance remains controversial. The efficacy and safety of ibrutinib monotherapy or combination therapy in patients with R/R DLBCL remain uncertain. The PubMed, CBM, MEDLINE, Cochrane Library, and Embase databases were searched from their inception to July 2021. The total complete remission rate (CRR) and overall response rate in R/R DLBCL patients treated with ibrutinib were 26% and 49%, respectively. The CRR of ibrutinib combination therapy was significantly higher than the ibrutinib monotherapy (45% vs. 19%). Moreover, the CRR of patients was 40% in double expressing lymphoma, 35% in central nervous system lymphoma, and 33% in nongerminal center B-cell-like (non-GCB) DLBCL, which was higher than the 8% in those with the GCB subtype. The pooled median PFS and overall survival were 5.57 and 10.17 months, respectively. GCB-DLBCL had the worst overall survival (5.1 months). Nevertheless, we found that combination regimens had no survival advantage compared with monotherapy (P > 0.05), indicating that combination therapy was only a transitional treatment and bridge for chimeric antigen receptor T cells or other treatments. Moreover, 12% of patients on ibrutinib combination therapy had ≥grade 3 adverse events compared with 9% on ibrutinib monotherapy. Ibrutinib monotherapy or combination therapy was safe and effective in treating R/R DLBCL with tolerable adverse reactions.

Synergistic effect of venetoclax and ibrutinib on ibrutinib-resistant ABC-type DLBCL cells.

Despite the widespread use of R-CHOP therapy in diffuse large B-cell lymphoma (DLBCL), the therapeutic efficacy for this disease remains suboptimal, primarily due to the heterogeneity of refractory and/or relapsed diseases. To address this challenge, optimization of DLBCL treatment regimens has focused on the strategy of combining an additional drug "X" with R-CHOP to enhance efficacy. However, the failure of R-CHOP combined with the BTK inhibitor ibrutinib in treating ABC-type DLBCL patients has raised significant concerns regarding ibrutinib resistance. While some studies suggest that venetoclax may synergize with ibrutinib to kill ibrutinib-resistant cells, the underlying mechanisms remain unclear. Our study aimed to validate the enhanced tumor-suppressive effect of combining ibrutinib with venetoclax against ibrutinib-resistant cells and elucidate its potential mechanisms. Our experimental results demonstrated that ibrutinib-resistant cells exhibited significant cytotoxicity to the combination therapy of ibrutinib and venetoclax, inducing cell apoptosis through activation of the mitochondrial pathway and inhibition of aerobic respiration. Furthermore, we validated the inhibitory effect of this combination therapy on tumor growth in in vivo models. Therefore, our study proposes that the combination therapy of ibrutinib and venetoclax is a promising treatment strategy that can be applied in clinical practice for ABC-type DLBCL, offering a new solution to overcome the urgent challenge of ibrutinib resistance.

Ibrutinib combination therapy for advanced gastrointestinal and genitourinary tumours: results from a phase 1b/2 study

BackgroundIbrutinib, a first-in-class inhibitor of Bruton’s tyrosine kinase, is approved for the treatment of various B-cell malignancies and chronic graft-versus-host disease. Based on encouraging preclinical data, safety and efficacy of ibrutinib combined with companion drugs for advanced renal cell carcinoma (RCC), gastric/gastroesophageal junctional adenocarcinoma (GC), and colorectal adenocarcinoma (CRC) were evaluated.MethodsIbrutinib 560 mg or 840 mg once daily was administered with standard doses of everolimus for RCC, docetaxel for GC, and cetuximab for CRC. Endpoints included determination of the recommended phase 2 dose (RP2D) of ibrutinib in phase 1b and efficacy (overall response rate [ORR] for GC and CRC; progression-free survival [PFS] for CRC) in phase 2.ResultsA total of 39 (RCC), 46 (GC), and 50 (RCC) patients were enrolled and received the RP2D. Safety profiles were consistent with the individual agents used in the study. Confirmed ORRs were 3% (RCC), 21% (GC), and 19% (CRC). Median (90% CI) PFS was 5.6 (3.9–7.5) months in RCC, 4.0 (2.7–4.2) months in GC, and 5.4 (4.1–5.8) months in CRC.ConclusionsClinically meaningful increases in efficacy were not observed compared to historical controls; however, the data may warrant further evaluation of ibrutinib combinations in other solid tumours.Trial registrationClinicalTrials.gov, NCT02599324.

MiR-28-based combination therapy impairs aggressive B cell lymphoma growth by rewiring DNA replication

Diffuse large B cell lymphoma (DLBCL) is the most common aggressive B cell lymphoma and accounts for nearly 40% of cases of B cell non-Hodgkin lymphoma. DLBCL is generally treated with R-CHOP chemotherapy, but many patients do not respond or relapse after treatment. Here, we analyzed the therapeutic potential of the tumor suppressor microRNA-28 (miR-28) for DLBCL, alone and in combination with the Bruton’s tyrosine kinase inhibitor ibrutinib. Combination therapy with miR-28 plus ibrutinib potentiated the anti-tumor effects of monotherapy with either agent by inducing a specific transcriptional cell-cycle arrest program that impairs DNA replication. The molecular actions of miR-28 and ibrutinib synergistically impair DNA replication by simultaneous inhibition of origin activation and fork progression. Moreover, we found that downregulation of the miR-28-plus-ibrutinib gene signature correlates with better survival of ABC-DLBCL patients. These results provide evidence for the effectiveness of a new miRNA-based ibrutinib combination therapy for DLBCL and unveil the miR-28-plus-ibrutinib gene signature as a new predictor of outcome in ABC-DLBCL patients.

Results from a Phase 1b/2 Study of Ibrutinib Combination Therapy in Advanced Urothelial Carcinoma.

Ibrutinib is a first-in-class Bruton's tyrosine kinase inhibitor approved for the treatment of various B-cell malignancies and chronic graft-versus-host disease. We evaluated the safety and efficacy of ibrutinib, alone or combined with standard-of-care regimens, in adults with advanced urothelial carcinoma (UC). Once-daily ibrutinib was administered orally at 840 mg (single-agent or with paclitaxel) or at 560 mg (with pembrolizumab). Phase 1b determined the recommended phase 2 dose (RP2D) of ibrutinib, and phase 2 assessed progression-free survival (PFS), overall response rate (ORR), and safety. Thirty-five, eighteen, and fifty-nine patients received ibrutinib, ibrutinib plus pembrolizumab, and ibrutinib plus paclitaxel at the RP2D, respectively. Safety profiles were consistent with those of the individual agents. The best-confirmed ORRs were 7% (two partial responses) with single-agent ibrutinib and 36% (five partial responses) with ibrutinib plus pembrolizumab. Median PFS was 4.1 months (range, 1.0-37.4+) with ibrutinib plus paclitaxel. The best-confirmed ORR was 26% (two complete responses). In previously treated patients with UC, ORR was higher with ibrutinib plus pembrolizumab than with either agent alone (historical data in the intent-to-treat population). ORR with ibrutinib plus paclitaxel was greater than historical values for single-agent paclitaxel or ibrutinib. These data warrant further evaluation of ibrutinib combinations in UC.

CTIM-34. PRELIMINARY SAFETY AND EFFICACY DATA ON TWO PATIENTS WITH RELAPSED/REFRACTORY CNS LYMPHOMA TREATED WITH EMAVUSERTIB (CA-4948) AND IBRUTINIB COMBINATION: A SUBSET ANALYSIS OF TAKEAIM LYMPHOMA TRIAL

Abstract BACKGROUND Emavusertib, an oral interleukin-1 receptor-associated kinase 4 (IRAK4) inhibitor, targets toll-like receptor (TLR) and interleukin-1 receptor (IL-1R) signaling pathway in B-cell proliferation. IRAK4 forms a Myddosome complex with MYD88 adaptor protein and drives overactivation of NF-κB, causing inflammation and tumor growth. Emavusertib has been reported to be well tolerated and active as monotherapy in heavily pretreated relapsed/refractory (R/R) non-Hodgkin lymphoma (NHL). In a murine PDX model of primary CNS lymphoma (PCNSL), emavusertib crossed the blood-brain barrier, resulting in tumor response and prolonged survival. In combination with Bruton tyrosine kinase (BTK) inhibitors, emavusertib showed in vivo anti-cancer synergy in B-cell NHL. METHODS This is an ongoing open-label trial (NCT03328078) in patients with R/R NHL. Currently, we are in the dose escalation portion of combination therapy to evaluate safety and efficacy following treatment of emavusertib at dose levels of 200 or 300mg BID with ibrutinib at full prescribed dose. As of May 6th, 2022, 13 patients have been treated with emavusertib+ibrutinib combination therapy. RESULTS Among the 13 patients, two were diagnosed with R/R PCNSL and had several prior lines of anti-cancer therapy. Emavusertib in combination with ibrutinib (560 mg daily) appeared to be well tolerated in these two subjects. One patient experienced Gr3 treatment-related adverse events (thrombocytopenia, muscle weakness, pain). The preliminary efficacy data demonstrated one CR and one SD. The patient who achieved CR after the combination therapy was originally intolerant to high-dose methotrexate based chemoimmunotherapy and did not achieve complete remission after switching to ibrutinib, providing early clinical evidence of CNS penetration and anti-tumor activity of emavusertib. CONCLUSION In R/R PCNSL, these preliminary data suggest that combination therapy has a tolerable safety profile with promising anti-cancer activity and may overcome ibrutinib resistance.

P654: IBRUTINIB PLUS VENETOCLAX IN PATIENTS WITH COMPLEX KARYOTYPE AND CHRONIC LYMPHOCYTIC LEUKEMIA

Background: In the largest study of Baliakas et al. (2019) the presence of at least 5 abnormalities, was associated with dismal clinical outcome, independently of the somatic hypermutation status and TP53 status. The presence of 3 or 4 aberrations is defined as clinically relevant in the absence of TP53. Studies by Kittai (2021) and Al-Sawaf (2020) showed the impact of karyotypic complexity on survival in patients with chronic lymphocytic leukemia (CLL) treated with ibrutinib or venetoclax. The complex karyotype (CK) is a topic that is being intensively researched, both in the aspect of increasing karyotypic complexity stratification and clonal evolution. Optimal therapy for patients with CLL has not yet been developed. The combination therapy of ibrutinib and venetoclax was superior to chlorambucil and obinutuzumab in terms of undetectable minimal residual disease (MRD) responses according to data from the GLOW trial (Tunir, 2021). The importance of achieving a complete response with undetectable MRD as the goal of therapy in CLL was proposed (Montserrat, 2005). Aims: The aim of our study is to evaluate the effectiveness of therapy with ibrutinib and venetoclax in combination for the patients with CLL and CK. Methods: This ambilinear observational study included patients with CLL with high genetic complexity (high-CK), defined as >=5 aberrations or CK (>=3 aberrations) in combination with a 17p deletion (CK+del17p). The first retrospective cohort included patients treated with ibrutinib monotherapy (Imono) to progression or intolerable toxicity since May 2015. The second prospective cohort included patients receiving ibrutinib in combination with venetoclax (IVen) since July 2019. Venetoclax therapy was started at the 3rd month of ibrutinib (from the escalation phase). Combination therapy was continued until a complete response, defined as three consecutive PET-CT-negative and MRD-negative results 3 months apart. If this criterion was not achieved at 24th month of therapy, venetoclax was discontinued and ibrutinib continued indefinitely. Results: Seventy-nine patients are included in the study. Twenty-nine patients in the first cohort and 50 patients in the second cohort. The characteristic is presented in Table. At the current follow-up periods, there were no significant differences in PFS and OS regarding a follow-up period <= 24 months (with the exception of death from COVID-19, since patients were not observed at parallel time intervals). In the group of patients treated with Imono, the majority of patients achieved partial remission or partial remission with lymphocytosis by 12 months. In 21 patients from Iven group, with a median follow-up of 7.4 months, a complete remission was achieved (72.4%); of these, 8 had unmeasurable MRD. Four patients did not complete the escalation period. There was a significant difference in the median MRD response achieved between 3 (log10>10) and 12 (log10<0,1) months in IVen group (p=0,03). In 2 patient from the IVen group progression of the disease was noted. Image:Summary/Conclusion: Combination therapy with ibrutinib and venetoclax is an effective oral regimen for high-risk patients with complex karyotype disorders. PFS in both groups is currently not significantly different, which is obviously due to the short follow-up period. Patients receiving the IVen regimen achieve a significantly better response, which paves the way for allogeneic transplantation in these patients.

Long-Term Sustained Responses Following Ibrutinib Discontinuation after Frontline Therapy with Obinutuzumab Plus Ibrutinib in Patients with Chronic Lymphocytic Leukemia

Single oral targeted therapies have emerged as a standard of care in chronic lymphocytic leukemia (CLL). However, accessibility, side effects, and financial burden associated with long term administration limit their clinical use. Mainly, it is unclear in what clinical situation discontinuation of oral therapy can be recommended. The combination of type II anti-CD20 antibody obinutuzumab-Gazyva® with ibrutinib (GI) has shown a significant progression-free survival benefit in patients (pts) with CLL, including those with high-risk genomic aberrations. We conducted a phase 1b/2, single-arm, open-label trial to evaluate the safety and efficacy of GI as first-line treatment in 32 CLL pts. We report the outcome in pts that discontinued ibrutinib (either after 3 years of sustained complete response (CR) as stipulated in the clinical protocol, or due to other reasons). CLL pts enrolled in this protocol were ≥65 years old, or unfit/unwilling to receive chemotherapy. Pts received GI for six cycles, followed by daily single-agent ibrutinib. The protocol was designed to ensure that pts with a sustained CR after 36 months were allowed to discontinue ibrutinib. The median age was 66 years (IQR 59-73), and 6% of the evaluated pts had 17p deletion. All pts were able to complete the six planned cycles of obinutuzumab. The combination regimen was well-tolerated, and the most common adverse events (&amp;gt;5% CTCAE grade 3-4) were neutropenia, thrombocytopenia, and hyperglycemia. The rate and severity of infusion-related reactions (IRR) were much lower than expected (Grade≥ 3, 3%), and pts without IRR had lower serum levels of cytokines/chemokines CCL3 (P=0.0460), IFN-γ (P=0.0457), and TNF-α (P=0.0032) after infusion. The overall response rate was 100%, with nine pts (28%) achieving a CR, and four pts (12.5%) with undetectable minimal residual disease (uMRD) in the bone marrow, defined as &amp;lt;10-4 CLL cells on multicolor flow cytometry. At a median follow-up of 35.5 months (IQR 24.5-42.7) after starting treatment, 91% of the enrolled pts remain in remission with a 100% overall survival. Sixteen pts have completed a long-term follow-up of 36 months. Six pts showed CR, with three of them achieving uMRD in the bone marrow. Ten of these pts were in PR, and only one had disease progression and started treatment for symptomatic stage I disease with obinutuzumab plus venetoclax. In total, thirteen pts (41%) have stopped ibrutinib, with a median time on treatment prior to discontinuation of 35 months. Five (16%) of these pts had CRs and discontinued after 36 months. Eight additional pts (25%) had PRs and discontinued ibrutinib without being eligible: three pts discontinued prior to 36 months due to toxicities, and five pts discontinued after 36 months (3 due to side effects, and 2 due to financially driven decision). One patient eligible to discontinue ibrutinib, decided to remain on treatment despite sustained CR. After a median follow up time following ibrutinib discontinuation of 8 months (IQR 3.5-17), only two out of 13 pts have progressed (10 and 17 months after Ibrutinib discontinuation). None of the pts that stopped ibrutinib after achieving a CR have shown signs of disease progression. Of note, the pharmaceutical sponsor provided ibrutinib for the first 36 months, after which pts or their insurer became financially responsible. This particular scenario could bias the discontinuation pattern compared to a real world experience. It also provided us with a perspective about diverse factors affecting the treatment choices of pts. In summary, the obinutuzumab plus ibrutinib combination therapy was well-tolerated, with a much lower IRR rate. Efficacy compares favorably with historical controls with all pts responding to therapy, no deaths associated with treatment or disease progression, and a longer than expected time-to-progression after discontinuation of ibrutinib. The rate of ibrutinib discontinuation was higher than reported in the literature, most likely influenced by the protocol design and financial decisions driven by the switch from sponsor-provided ibrutinib to insurance or self-paid medication. Our observations regarding safety, efficacy and lack of disease progression after ibrutinib discontinuation are encouraging, and warrant confirmation in long-term prospective studies. Clinicaltrials.gov Identifier NCT02315768. Funding: Pharmacyclics LLC. Disclosures Choi: AbbVie: Consultancy, Speakers Bureau. Amaya-Chanaga:AbbVie: Ended employment in the past 24 months, Other: Research performed while employed as an investigator of this study at UCSD.. Kipps:Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Castro:Kite Pharma: Research Funding; Pharmacyclics: Research Funding; Fate Therapeutics: Research Funding.

Changes in primary and secondary hemostasis in patients with CLL treated with venetoclax and ibrutinib

Bleeding is a common adverse event following ibrutinib monotherapy. However, it remains unclear how hemostasis is affected by venetoclax in combination with ibrutinib. Here we investigated hemostasis in patients with chronic lymphocytic leukemia (CLL) at baseline, during ibrutinib monotherapy, and during venetoclax and ibrutinib combination therapy or venetoclax monotherapy. Primary hemostasis, assessed by Multiplate using adenosine diphosphate (ADP), arachidonic acid (AA), and thrombin receptor agonist peptide (TRAP-6), was impaired in all CLL patients at baseline, remained unchanged upon ibrutinib monotherapy, and improved significantly following venetoclax added to ibrutinib or as monotherapy. Secondary hemostasis assessed by thromboelastography (TEG) was normal and unchanged throughout treatment. The frequency of clinical bleeding events was the highest during ibrutinib monotherapy, in line with the demonstrated improved primary hemostasis upon addition of venetoclax, thus pointing toward a treatment option for CLL patients with increased bleeding risk.

Pneumocystis jirovecii pneumonia and institutional prophylaxis practices in CLL patients treated with BTK inhibitors

Opportunistic infections (OIs), such as Pneumocystis jirovecii pneumonia (PJP), have been reported in chronic lymphocytic leukemia (CLL) patients treated with ibrutinib, and are an important cause of morbidity and mortality. Currently, there are no international consensus guidelines regarding the use of antimicrobial prophylaxis for OIs, and in particular PJP, in CLL patients treated with Bruton tyrosine kinase inhibitors (BTKi's). We evaluated the frequency of PJP in CLL patients at our institution who were treated with BTKi's, and assessed the impact of prophylaxis on reducing the risk of PJP. We identified 217 patients treated with BTKi's, consisting of 3 cohorts: 143 patients on either BTKi monotherapy with ibrutinib or acalabrutinib, 17 patients receiving ibrutinib combination therapy with umbralisib as part of a clinical trial, and 57 patients receiving ibrutinib in combination with standard chemotherapy, also as part of a clinical trial. Forty-one percent of patients on BTKi monotherapy received prophylaxis, which was given at the discretion of the treating physician. The prevalence of PJP in all patients not on prophylaxis was 3.4% (3 of 87), and, specifically in BTKi-monotherapy patients not on prophylaxis, the PJP prevalence was 2.4% (2 of 85). PJP prophylaxis was effective, as there were no cases of PJP in patients on prophylaxis (0 of 130). The relatively low prevalence of PJP in our study population suggests that routine prophylaxis may not be indicated in CLL patients on BTKi therapy.

T-Cell Clonal Expansion and Activation Associated with Durable Clinical Response to Dual BTK and CDK4/6 Inhibitor Therapy in Mantle Cell Lymphoma

T-Cell Clonal Expansion and Activation Associated with Durable Clinical Response to Dual BTK and CDK4/6 Inhibitor Therapy in Mantle Cell Lymphoma

In Vivo Evidence of in Situ Cell Death Preferentially Occurring in CLL Patients with Minimal Lymphocytosis By the Diminished BCL2 and Loss of T Cell Support after Ibrutinib Treatment

Chronic lymphocytic leukemia (CLL) patients receiving the BTK inhibitor ibrutinib develop lymphocytosis. Prolonged lymphocytosis is associated with good prognosis in both treatment-naïve (TN) and relapsed/refractory (R/R) patients, although in general R/R cases have higher lymphocytosis peaks. Because the degree and duration of the elevations vary between patients, lymphocytosis is likely not caused solely by release of cells from tissue niches. Mathematical modeling suggests less profound lymphocytosis of shorter duration is due to loss of tissue resident cells in situ. To address contributions of local elimination and egress to the periphery, we performed phenotypic and functional analyses of cell migration, survival/growth and interactions of CLL B and T cells, and correlated these results with ibrutinib induced T and B cell lymphocytoses.Studies of CLL B cell lymphocytosis were performed with TN (17 U- and 11 M-CLL) and R/R (5 U-CLL) cases receiving single-agent ibrutinib therapy. Faster resolution of lymphocytosis was seen in TN U-CLL than in M-CLL cases (P = 0.008). Conversely, all 5 R/R U-CLL patients exhibited considerably longer lymphocytosis upon ibrutinib use (median time to normalization in TN vs R/R U-CLL: 17 vs 77 days, P = 0.01). Nevertheless, after treatment, all cases showed reduced surface levels of chemokine receptors (CXCR5, CXCR7, CCR7), integrins (CD11a, CD49d) and elevated numbers of CXCR4 molecules that were non-functional based on impaired receptor signaling and recycling/internalization. Also, CLL B cells collected after 2 cycles of ibrutinib treatment exhibited impaired chemotaxis to lymphoid tissues in alymphoid NSG mice. However, none of these changes differed between CLL cases with minimal or prolonged lymphocytosis.We next investigated ibrutinib induced changes in tissue resident cells in a xenograft mouse model. Activated autologous T cells and PBMC prepared from TN (2 U- and 3 M-CLL) and R/R (1 U-CLL) patients were injected into NSG mice. 14 days later, mice were given ibrutinib daily for 2 weeks. Ibrutinib significantly inhibited CLL B cell growth in spleens in all 5 TN cases but to a much greater extent in U-CLL than M-CLL (P = 0.01). The R/R case also had reduced CLL B cell numbers in spleens after treatment, but this was not statistically significant. Molecules controlling CLL B cell survival were then examined in 15 TN and 5 R/R cases. Ibrutinib reduced BCL2 protein levels in TN patients with minimal lymphocytosis but not those with prolonged lymphocytosis (P < 0.001) or R/R patients (P = 0.017). These data suggest those tissue resident cells that are lost after ibrutinib therapy have reduced BCL2 protein levels.In CLL T cells, ibrutinib targets ITK, an enzyme involved in T cell migration and function. Indeed, we found ibrutinib induced T cell lymphocytosis in the same cohort of patients described above. Shorter T cell lymphocytosis was seen in TN U- but not M-CLL or R/R cases (19.6±4 vs 44.3±13, P = 0.04). Ibrutinib blocked T cell chemotaxis in all the cases, but only significantly inhibited T cell growth of TN U-CLL cases in the same xenograft studies. The loss of T cells correlates with the greater inhibition of CLL B cells observed in TN U-CLL rather than in M-CLL cases. Supporting this finding, patients with minimal B cell lymphocytosis also had rapid resolution of T cell lymphocytosis. These data indicate ibrutinib blocked T cell growth in situ, especially in TN U-CLL patients. The loss of T cells further enhances CLL B cell death in tissues after ibrutinib treatment as autologous T cells can protect U-CLL cells from apoptosis by upregulating BCL2.Collectively, our findings suggest that although ibrutinib promotes T and B cell egress in almost all the CLL cases, patients with prolonged lymphocytosis after ibrutinib treatment have better cell survival in situ even after loss of tumor microenvironment contact. In situ cell death after ibrutinib treatment preferentially occurs in TN U-CLL but not in TN M-CLL and R/R cases, in part due to loss of BCL2 and of the support from non-neoplastic immune cells like T cells, documenting that these beneficial actions of ibrutinib are intimately involved in the numbers of lymphocytes that circulate after drug administration. Finally, our data are consistent with the previous report that ibrutinib increases leukemic cell sensitivity to venetoclax, providing a strong rationale for combination therapy of ibrutinib and venetoclax in CLL. DisclosuresBarrientos:Janssen: Consultancy; Gilead: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding. Burger:Gilead: Research Funding; Roche: Other: Travel, Accommodations, Expenses; Janssen: Consultancy, Other: Travel, Accommodations, Expenses; Portola: Consultancy; Pharmacyclics, LLC, an AbbVie Company: Research Funding.

A phase 1b/2 study of ibrutinib combination therapy in selected advanced genitourinary and gastrointestinal tumors.

TPS2600Background: For patients with advanced genitourinary (GU) and gastrointestinal (GI) tumors, effective treatment options are limited. Ibrutinib (ibr) is a first-in-class, covalent inhibitor o...

Ibrutinib (PCI-32765) Antagonizes Rituximab-Dependent NK-Cell Mediated Cytotoxicity

IntroductionIbrutinib is an irreversible inhibitor of Bruton's tyrosine kinase (BTK) with promising clinical activity in phase I/II clinical trials in CD20+ B-cell malignancies for which rituximab-combination chemotherapy is today's standard of care. Given homology between BTK and interleukin-2 inducible tyrosine kinase (ITK), we recently confirmed based on molecular and phenotypic analysis that ibrutinib irreversibly binds ITK (Dubovsky J, et al: Blood 2013). ITK expression in FcR-stimulated NK cells leads to increased calcium mobilization, granule release, and cytotoxicity (Khurana D et al: J Immunol 2007). As FcR stimulation is requisite for antibody-dependent NK-cell mediated cytotoxicity (ADCC), we investigated if ibrutinib influenced rituximab's anti-lymphoma activity as well as trastuzumab's anti-HER2+ breast cancer activity. MethodsRituximab and trastuzumab-dependent NK-cell mediated cytotoxicity was assessed using lymphoma and HER2+ breast cancer cell lines. In vitro NK cell cytokine secretion, degranulation and cytotoxicity were assessed by IFN-g release, CD107a mobilization and chromium release. Xenotransplant lymphoma and breast cancer models in athymic, nu/nu mice were used to assess efficacy of ibrutinib and rituximab or trastuzumab combination regimens. Using an autologous system from patients with chronic lymphocytic leukemia (CLL), inhibition of NK cell function was compared between ibrutinib and CGI-1746 (Di Paolo JA, et al: Nature Chem Biol 2011), a previously reported selective BTK inhibitor lacking ITK inhibitory function. ResultsFcR-stimulated NK cells following exposure to rituximab-coated lymphoma cells express high and moderate levels of ITK and BTK, respectively. Ibrutinib inhibited both rituximab- and trastuzumab-induced NK cell cytokine secretion in a dose-dependent manner at 0.1 and 1mM of ibrutinib in vitro (Fig 1A *p=.009, **p=.001, ***p<.001). Similarly, ibrutinib prevented FcR-stimulated NK cell degranulation by ∼60% and ∼90% at 0.1 and 1mM (Fig 1B *p=.013, **p=.017, ***p=.002, ****p=.001). In vitro cytotoxicity of rituximab-coated, chromium-labeled lymphoma cells was observed in an NK cell-independent and ibrutinib-concentration dependent manner (Fig 1C *p<.001, **p=.045). In contrast, in vitro cytotoxicity of trastuzumab-coated, chromium-labeled breast cancer cells was inhibited in an ibrutinib dose-dependent manner (Fig 1C ***p=.036, ****p=.010). Abrogation of trastuzumab-dependent NK cell-mediated cytotoxicity was confirmed in vivo with concurrent ibrutinib daily dosing for 2 weeks during trastuzumab treatment, 4 doses, as measured by tumor growth and survival (Fig 2A, *p<.001; Fig 2B *p=.18). Concurrent ibrutinib daily dosing for 2 weeks during 4 doses of rituximab therapy, similarly, antagonized rituximab's efficacy in tumor growth and survival, with anti-lymphoma activity of the combination equivalent to ibrutinib monotherapy (Fig 2C *p=.049, **p=.032; Fig 2D *p=.29). Sequential ibrutinib for 1 week followed by 2 doses of rituximab, or sequential rituximab (2 doses) followed by ibrutinib for 1 week resulted in restored anti-lymphoma activity superior to concurrent combination therapy of ibrutinib for 2 weeks and 4 doses of rituximab (Fig 2E *p<.001; Fig 2F *p<.001). Autologous CLL samples, n=6, confirmed similar effect as observed with lymphoma cell lines of 0.1 and 1mM of ibrutinib resulting in in vitro inhibition of NK cell degranulation and cytotoxicity by ∼65% and ∼85%, respectively. Interestingly, in vitro, CGI-1746 had no antagonistic effect on ADCC against rituximab treated targets (CLL cells and Raji lymphoma cell line). [Display omitted] [Display omitted] ConclusionsPreclinical investigation of a combination therapy currently in Phase II and III clinical trials, adding a promising novel agent, ibrutinib, to a current standard of care, rituximab, for the treatment of B-cell lymphomas, surprisingly results in antagonistic effects. We demonstrate that the abrogation of both rituximab's and trastuzumab's anti-tumor efficacy is a result of ibrutinib's inhibition of FcR-stimulated NK cell function, specifically ADCC. Selective BTK inhibitors or alternative ibrutinib dosing schedules, sequential versus concurrent, may preserve the anti-lymphoma efficacy of both agents. Disclosures:Buggy:Pharmacyclics: Employment, Equity Ownership.