Exposure-response relationships of venetoclax in combination with carfilzomib and dexamethasone in relapsed/refractory t(11;14) multiple myeloma patients.

Venetoclax is a first in class BCL-2 inhibitor, currently under investigation for the treatment of t(11;14) multiple myeloma (MM). The objective of this analysis was to characterize the exposure-efficacy and exposure-safety relationships of venetoclax when combined with carfilzomib and dexamethasone (VenKd) in t(11;14)-positive relapsed or refractory (R/R) MM patients from a phase 2 study. Fifty-seven patients receiving VenKd or Kd were included in the analysis. Efficacy endpoints included progression-free survival and clinical response rates of overall response, very good partial response or better and complete response or better. Grade ≥ 3 neutropenia, Grade ≥ 3 infections, Grade ≥ 3 treatment-emergent adverse events and any grade serious treatment-emergent adverse events were evaluated. The analysis demonstrated that adding venetoclax to Kd resulted in increased ORR, ≥VGPR and ≥ CR rates compared to the control arm. Within the venetoclax treatment arms (VenKd), no significant exposure-efficacy relationships were observed for ORR and ≥ VGPR rates. Higher ≥ CR rates trended with higher venetoclax exposures. While both 400 mg and 800 mg venetoclax in VenKd arms were generally tolerated, higher rates of Grade ≥ 3 neutropenia were observed with higher venetoclax exposures. Higher venetoclax exposures however were not associated with increased rates of Grade ≥ 3 treatment-emergent adverse events, Grade ≥ 3 infections, or serious treatment-emergent adverse events (any grade). These results confirm the benefit of adding venetoclax to carfilzomib and dexamethasone and support continued evaluation of venetoclax 400-800 mg once daily in this combination in t(11;14)-positive R/R MM patients. NCT02899052 registered April 18, 2017.

Venetoclax in biomarker-selected multiple myeloma patients: Impact of exposure on clinical efficacy and safety.

Venetoclax, a potent BCL-2 inhibitor, is currently under development for treatment of t(11;14) Multiple myeloma (MM). The objective of this research was to investigate the exposure-response relationships of venetoclax for a phase 1/2 study evaluating venetoclax monotherapy or in combination with dexamethasone in relapsed or refractory MM. A total of 117 patients receiving venetoclax at 300, 600, 800, 900, or 1200 mg were included in the analysis. The impact of venetoclax exposures on efficacy (objective response rate [ORR], progression-free survival [PFS] and overall survival [OS]) as well as safety (treatment-emergent adverse effects (grade ≥3) of neutropenia, infection, and any grade of serious treatment-emergent adverse effects) was evaluated. In the t(11;14)-positive subpopulation, venetoclax exposure relationships to PFS and OS indicated a trend of longer PFS and OS with higher exposures. Moreover, logistic regression analyses for clinical response (ORR and ≥VGPR rate) demonstrated a statistically significant (p < 0.05) relationship with exposure. Evaluation of the exposure-safety relationships demonstrated a lack of a relationship between venetoclax exposures (AUCavg ) and grade ≥3 infections, grade ≥3 neutropenia, grade ≥3 treatment-emergent adverse events or any grade serious treatment-emergent adverse events. These findings support further study of venetoclax at 800 mg QD dose in combination with dexamethasone in the t(11;14)-positive patient population where increased efficacy was observed without an increase in safety events.Clinical Trial: NCT01794520 registered 20 February 2013.

Venetoclax pharmacokinetics in participants with end-stage renal disease undergoing haemodialysis.

AIMS: Renal insufficiency is a common comorbidity in patients with haematological malignancies. This study aimed to assess how end-stage renal disease (ESRD) might affect the pharmacokinetics of venetoclax, a Bcl-2 inhibitor, in participants with ESRD undergoing haemodialysis. METHODS: Venetoclax was administered as a single 100-mg dose to 6 female participants with ESRD (estimated glomerular filtration rate <15 mL/min) both prior to haemodialysis and between haemodialysis days and 7 healthy female participants with normal renal function (estimated glomerular filtration rate >90 mL/min). Intensive pharmacokinetic and protein binding samples were collected from all participants. Arterial and venous samples were collected from ESRD participants during haemodialysis to assess the effect of haemodialysis on venetoclax pharmacokinetics. Pharmacokinetic parameters were estimated using noncompartmental methods. RESULTS: There was no difference in plasma venetoclax concentrations between arterial and venous samples, suggesting that haemodialysis did not affect the pharmacokinetics of venetoclax. The fraction unbound (fu ) of venetoclax was ~2-fold higher for participants with ESRD compared to participants with normal renal function. The unbound maximum plasma concentration and area under the plasma concentration-time curve from time 0 to 48 h were comparable between ESRD and normal function groups. The mean half-life ranged from 10.4 to 12.2 h across groups, demonstrating that ESRD did not affect the half-life of venetoclax. No new safety signals were observed during this study. CONCLUSION: ESRD and dialysis do not alter unbound venetoclax plasma concentrations. No pharmacokinetics driven dose adjustment is needed for patients with renal insufficiency.

A formal vinylic substitution reaction for the synthesis of α,ß-unsaturated enol esters and their anticancer potential.

Arylsulfonyl group-bearing α,ß-unsaturated enol esters were readily assembled via the Cs2CO3-mediated union of 2-bromoallyl sulfones and cinnamic acids. The overall transformation is equivalent to an sp2 carbon-oxygen coupling reaction, and therefore constitutes a formal vinylic substitution. Several of the products display promising levels of antiproliferative activities higher than that of the anticancer drug carboplatin. Thiophenol reacted with 2-bromoallyl sulfones under identical conditions to afford α-thiophenyl-α'-tosyl acetone via an apparent aerial oxidation.

Outcome of tailored therapy in rheumatic heart disease with persistent atrial fibrillation (RHD-AF).

INTRODUCTION: Rheumatic heart disease with persistent atrial fibrillation (RHD-AF) is associated with increased morbidity. However, there is no standardized approach for the maintenance of sinus rhythm (SR) in them. We aimed to determine the utility of a stepwise approach to achieve SR in RHD-AF. METHODS: Consecutive patients with RHD-AF from July 2021 to August 2023 formed the study cohort. The stepwise approach included pharmacological rhythm control and/or electrical cardioversion (Central illustration). In patients with recurrence, additional options included AF ablation or pace and ablate strategy with conduction system pacing or biventricular pacing. Clinical improvement, NT-proBNP, 6-Minute Walk Test (6MWT), heart failure (HF) hospitalizations, and thromboembolic complications were documented during follow-up. RESULTS: Eighty-three patients with RHD-AF (mean age 56.13 ± 9.51 years, women 72.28%) were included. Utilizing this approach, 43 (51.81%) achieved and maintained SR during the study period of 11.04 ± 7.14 months. These patients had improved functional class, lower NT-proBNP, better distance covered for 6MWT, and reduced HF hospitalizations. The duration of AF was shorter in patients who achieved SR, compared to those who remained in AF (3.15 ± 1.29 vs 6.93 ± 5.23, p = 0.041). Thirty-five percent (29) maintained SR after a single cardioversion over the study period. Only one underwent AF ablation. Of the 24 who underwent pace and ablate strategy, atrial lead was implanted in 22 (hybrid approach), and 50% of these achieved and maintained SR. Among these 24, none had HF hospitalizations, but patients who maintained SR had further improvement in clinical and functional parameters. CONCLUSIONS: RHD-AF patients who could achieve SR with a stepwise approach, had better clinical outcomes and lower HF hospitalizations.

Venetoclax exposure-efficacy and exposure-safety relationships in patients with treatment-naïve acute myeloid leukemia who are ineligible for intensive chemotherapy.

This study evaluated venetoclax population pharmacokinetics (popPK) in patients with treatment-naïve acute myeloid leukemia and assessed the relationship between venetoclax exposure and clinical response for venetoclax in combination with either a hypomethylating agent (HMA) or low-dose cytarabine (LDAC). A total of 771 patients who received venetoclax from 5 Phase 1-3 studies were included in the popPK model. Exposure-response analyses included data from 575 patients for venetoclax/placebo plus HMA and 279 patients for venetoclax/placebo plus LDAC. The popPK model successfully characterized venetoclax plasma concentrations over time and confirmed venetoclax exposure did not vary significantly with age, weight, sex, mild to moderate hepatic impairment, or mild to severe renal impairment. Asian patients had 67% higher mean relative bioavailability than non-Asian patients, however the range of exposures in Asian patients was similar to non-Asian patients. For all efficacy endpoints with both treatment combinations, efficacy was higher in the venetoclax treatment groups compared with the respective control arm of placebo plus azacitidine or LDAC. Within patients who received venetoclax, no significant exposure-efficacy relationships were identified for either treatment combination, indicating that the beneficial effects of venetoclax were already maximized in the dose ranges studied. There was no apparent effect of venetoclax exposure on treatment-emergent Grade ≥3 thrombocytopenia or infections for either combination. Rates of treatment-emergent Grade ≥3 neutropenia were higher in the venetoclax treatment arms compared with the respective control arms; however, within patients who received venetoclax, there was only a shallow relationship or no apparent relationship with venetoclax exposure for venetoclax plus HMA or LDAC, respectively. Along with the efficacy and safety data previously published, the exposure-response analyses support the venetoclax dose regimens of 400 mg once daily (QD) plus HMA and 600 mg QD plus LDAC in treatment-naïve AML patients who are ineligible for intensive chemotherapy.

Benzannulation Reactions: A Case for Perspective Change From Arene Decoration to Arene Construction.

Benzannulation reactions involve construction of a benzene ring from acyclic precursors. This class of reactions offer a versatile and often superior alternative to aromatic substitution for construction of substituted arenes. Selected pioneering and recent reports of various benzannulation reactions are categorised and discussed in this review.

Recent developments in the chemistry of allenyl sulfones.

Allenyl sulfones are versatile building blocks that readily partake in a variety of transformations such as Michael additions, rearrangements, cycloadditions, electrophilic additions and redox reactions. Selected recent developments in the preparation and various reactions of allenyl sulfones are presented.

Regioselective synthesis of arylsulfonyl heterocycles from bromoallyl sulfones via intramolecular Heck coupling reaction.

Indoles, benzofurans and benzosultams endowed with arylsulfonyl groups were prepared in two steps from 2-bromoallyl sulfones. ortho-Halosulfonamides and ortho-iodophenol reacted with 2-bromoallyl sulfones in the presence of cesium carbonate to furnish products resulting from a formal vinylic substitution reaction. Palladium-catalyzed intramolecular Heck reaction of these adducts furnished sulfonylated indoles, benzosultams and benzofurans. Isomerization of the double bond participating in the Heck reaction under basic conditions led to the formation of two isomeric products in two cases. Conditions for selectively accessing each of the regioisomeric indoles were developed.

Optimizing venetoclax dose in combination with low intensive therapies in elderly patients with newly diagnosed acute myeloid leukemia: An exposure-response analysis.

The objective of this research was to characterize the venetoclax exposure-efficacy and exposure-safety relationships and determine its optimal dose in elderly patients with newly diagnosed acute myeloid leukemia (AML) receiving venetoclax in combination with low intensity therapies (hypomethylating agent [HMA; azacitidine or decitabine] or low-dose cytarabine [LDAC]). A total of 212 patients from the HMA study and 92 patients from the LDAC study were included in the exposure-safety analyses. Those who received at least one dose of venetoclax and had at least one measurable response (201 and 83 in the HMA and LDAC studies, respectively) were included in the exposure-efficacy analyses. The probability of response based on International Working Group (IWG) for AML response criteria, adverse events of grade 3 or worse neutropenia or infection or a serious adverse event was modeled using logistic regression analyses to characterize the venetoclax exposure-response relationships. In combination with an HMA, increasing concentrations of venetoclax, up to those associated with a less than or equal to 400-mg once daily (QD) dose, were associated with a higher probability of response, with a trend for flat or decreasing probabilities of response thereafter. In combination with LDAC, increasing concentrations of venetoclax were associated with higher probabilities of response, with no plateau observed. Increasing concentrations of venetoclax were not associated with increasing probability of any safety event except for a slight increase in grade 3 or worse infections with HMAs; however, tolerability issues were observed at doses of greater than or equal to 800 mg QD in each study. Exposure-response analyses support the use of venetoclax 400 mg QD in combination with an HMA and 600 mg QD in combination with LDAC (ie, the next highest dose evaluated below 800 mg in each combination) to safely maximize the probability of response in elderly patients with newly diagnosed AML.

Nucleophile-Initiated Catalytic and Multicomponent Reactions.

A number of well-known reactions, proceed through the intermediacy of dipolar/zwitterionic species generated via the addition of a neutral nucleophile with an unsaturated electrophile. A mechanistic understanding of these reactions was made possible by seminal contributions of Huisgen. The design of novel reactions based on such dipolar species was, however, not pursued in detail for a long time. Our efforts to exploit various reactivity profiles available for the zwitterionic/dipolar intermediates have resulted in the discovery of a large number of novel, convenient protocols to access a wide variety of products. The nucleophilic initiators may participate in the reaction or play a mediating role depending upon the nature of nucleophile, its quantity and the reaction conditions. In a majority of these transformations two electrophilic components, that would normally be inert towards each other, are combined by the intermediacy of a nucelophile. A brief summary of such nucleophile-initiated novel reactions that were developed in our research group are described. Reactions involving a variety of nucleophiles such as phosphines, pyridine, quinoline, isoquinoline, isocyanides, dimethoxycarbene and N-heterocyclic carbenes (NHCs) are discussed.

Facile synthesis of biarylmethanes and tetrasubstituted arenes via a base-mediated [3 + 3] benzannulation reaction of Morita-Baylis-Hillman adducts and unsaturated sulfones.

A facile DBU-mediated [3 + 3] benzannulation reaction of 1,3-bis-sulfonyl propenes and Morita-Baylis-Hillman (MBH) bromides is described. The benzannulation reaction afforded bis-sulfonyl biarylmethanes/arenes with complete regioselectivity. The products may be converted readily into corresponding benzophenones via site-selective benzylic oxidation.

Gold-catalysed regioselective cascade cycloisomerisation reactions of aza-enediynes for the synthesis of substituted benzoisoquinoline derivatives.

Aza-enediynes underwent a facile, regioselective gold-catalysed cascade cycloisomerisation to furnish dihydrobenzo[f]isoquinoline derivatives in excellent yields. The aza-enediynes were conveniently prepared via a formal vinylic displacement reaction of allyl bromosulfones. The latter functioned as a stable and easily accessible synthetic equivalent of allenyl sulfone.

Effects of chronic kidney disease stage 4, end-stage renal disease, or dialysis on the plasma concentrations of ombitasvir, paritaprevir, ritonavir, and dasabuvir in patients with chronic HCV infection: pharmacokinetic analysis of the phase 3 RUBY-I and RUBY-II trials.

PURPOSE: To characterize the pharmacokinetics of ombitasvir, paritaprevir, ritonavir, dasabuvir, and ribavirin in hepatitis C virus (HCV)-infected patients with chronic kidney disease stage 4 (CKD4) or end-stage renal disease (ESRD), including those on dialysis, in the open-label phase 3 RUBY-I and RUBY-II studies. METHODS: Patients (n = 18 CKD4, n = 68 ESRD) received ombitasvir/paritaprevir/ritonavir 25/150/100 mg once daily ± dasabuvir 250 mg twice daily ± ribavirin 200 mg once daily for 12 or 24 weeks. Intensive pharmacokinetic samples were collected from ten patients; sparse samples were collected from all patients. Arterial and venous samples were collected from three patients during hemodialysis. Area under the plasma concentration-time curve (AUC) was estimated using noncompartmental analyses for intensive data, and steady-state trough concentrations (Ctrough) were obtained from the sparse data. Pharmacokinetic results from RUBY-I and RUBY-II were compared empirically to historical data. RESULTS: The AUC values of ombitasvir, paritaprevir, ritonavir, and dasabuvir were comparable between CKD4 and ESRD patients and were within the range of values observed in historical studies; dialysis had no effect on drug exposures. Ribavirin was extracted during hemodialysis but had similar exposures on dialysis and non-dialysis days. Individual steady-state Ctrough values for each drug overlapped between CKD4 and ESRD patients, and values in both groups were similar to historical values. CONCLUSION: Plasma concentrations of ombitasvir, paritaprevir, ritonavir, and dasabuvir were not altered by renal impairment or dialysis, suggesting these agents can be administered to HCV-infected CKD4 or ESRD patients, including those on dialysis, without dose adjustment. TRIAL REGISTRATION: Clinicaltrials.gov identifiers: NCT02207088 (RUBY-I) and NCT02487199 (RUBY-II).

Use of depth of response to predict progression-free survival in relapsed or refractory multiple myeloma: Evaluation of results from 102 clinical trials.

Progression-free survival (PFS) is the standard endpoint for demonstration of clinical effectiveness of novel therapies in relapsed or refractory multiple myeloma (RRMM). However, the long evaluation times for PFS limits its usefulness in the development of new therapies. Therefore, the objective of this analysis was to determine the relationship between response rates and median PFS in RRMM. A database was systematically developed from 268 identified RRMM trials reported from 1999 to 2016. Evaluated covariates for the relationship between response rates and PFS included age, sex, drug class(es), and number of drug classes. One-hundred two (102) trials involving 136 cohorts were included in the meta-analysis, representing 13 322 patients in total. Regression analysis using response rates and median PFS indicated that the correlation between very good partial response (VGPR) or better and median PFS was higher (R2  = 0.63) than the separately analyzed correlations between clinical benefit, overall response, or complete response rate and median PFS (R2  = 0.47 - 0.52). Subsequent covariate analysis revealed that treatment with an immunomodulatory imide drug (IMiD) further improved the relationship (R2  = 0.69), with a longer median PFS at a given VGPR or better rate when at least 1 drug treatment was an IMiD. Number of drug classes was not found to alter this relationship. In conclusion, VGPR or better rate can be used to predict the median PFS, with adjustment for the additional PFS provided by an IMiD.

Relationship between response rates and median progression-free survival in non-Hodgkin's lymphoma: A meta-analysis of published clinical trials.

Demonstration of clinical effectiveness of a non-Hodgkin's lymphoma (NHL) treatment generally involves determination of progression-free survival (PFS). However, the long evaluation time of PFS limits its utility to make timely decisions in drug development. Therefore, the objective of this analysis was to determine the relationship between response rates and median PFS in NHL. A database was systematically developed from 513 identified NHL trials reported from 1996 to 2015. Potential predictors of the relationship between response rates and PFS were evaluated, including age, sex, treatment, percentage of treatment-naïve patients, and subtype of NHL. Seventy-three trials involving 86 cohorts were included in the meta-analysis. Linear regression analysis using logit of response rates and logarithm of median PFS indicated that the correlation between overall response rate (ORR) and median PFS was higher (R2  = 0.70) when compared to that of complete response (CR) rate and median PFS (R2  = 0.57). Furthermore, the correlation was improved with the addition of percentage of treatment-naïve patients and percentage of patients with follicular lymphoma (FL) (P < .005) between ORR and median PFS (R2  = 0.78), and between CR rate and median PFS relationship (R2  = 0.74). Treatment was not found to alter this relationship. In summary, ORR is as good as CR rate in predicting median PFS. Moreover, longer median PFS is expected in the trials including treatment-naïve and/or FL patients at a given ORR/CR rate. The determined relationship can be used to project the median PFS based on ORR or CR rate.

Clinical evaluation of P-glycoprotein inhibition by venetoclax: a drug interaction study with digoxin.

1. Venetoclax is a novel, small molecule B-cell lymphoma-2 (BCL-2) inhibitor that has demonstrated clinical efficacy in a variety of haematological malignancies. Since venetoclax is an inhibitor of P glycoprotein (P-gp) transporter, a study was conducted in healthy, female volunteers to evaluate the effect of venetoclax on the pharmacokinetics of digoxin, a P-gp probe substrate. 2. Volunteers received a single oral dose of digoxin (0.5 mg) with or without a single oral dose of venetoclax (100  mg). Serial blood samples were obtained for pharmacokinetic assessments of digoxin and venetoclax and serial urine samples were obtained for measurement of digoxin concentrations. Safety was assessed throughout the study. 3. Coadministration of digoxin and venetoclax increased digoxin maximum observed plasma concentration (Cmax) by 35% and area under the plasma-concentration time curve (AUC0-∞) by 9%. Digoxin half-life, renal clearance and the fraction excreted unchanged in urine remained relatively similar. The results of this study indicate that venetoclax can increase the concentrations of P-gp substrates. Narrow therapeutic index P-gp substrates should be administered six hours prior to venetoclax to minimise the potential interaction.

Guiding dose adjustment of amlodipine after co-administration with ritonavir containing regimens using a physiologically-based pharmacokinetic/pharmacodynamic model.

Amlodipine, a commonly prescribed anti-hypertensive drug, shows increased systemic exposure with cytochrome P450 (CYP) 3A inhibitors. Ritonavir (RTV) is a potent mechanism-based and reversible CYP3A inhibitor and moderate inducer that is used as a pharmacokinetic enhancer in several antiviral treatment regimens. Drug-drug interaction (DDI) between RTV and amlodipine is due to mixed inhibition and induction of CYP3A4, which is challenging to predict without a mechanistic model that accounts for the complexity of both mechanisms occurring simultaneously. A novel physiologically-based pharmacokinetic (PBPK) model was developed for amlodipine, and the model was verified using published clinical PK and DDI data. The verified amlodipine PBPK model was linked to a pharmacodynamics model that describes changes in systolic blood pressure (SBP) during and after co-administration with RTV. The magnitude and time course of RTV effects on amlodipine plasma exposures and SBP were evaluated, to provide guidance on dose adjustment of amlodipine during and after co-administration with RTV-containing regimens. Model simulations suggested that the increase in amlodipine's plasma exposure by RTV diminishes by approximately 80% within 5 days after the last dose of RTV. PBPK simulations suggested that resuming a full dose of amlodipine [5 mg once daily (QD)] immediately after RTV's last dose would decrease daily average SBP by a maximum of 3.3 mmHg, while continuing with the reduced dose (2.5 mg QD) for 5 days after the last dose of RTV would increase daily average SBP by a maximum of 5.8 mmHg. Based on these results, either approach of resuming amlodipine's full dose could be appropriate when combined with appropriate clinical monitoring.

Pharmacokinetic Evaluation of Darunavir Administered Once or Twice Daily in Combination with Ritonavir or the Three-Direct-Acting Antiviral Regimen of Ombitasvir/Paritaprevir/Ritonavir and Dasabuvir in Adults Coinfected with Hepatitis C and Human Immunodeficiency Viruses.

The three-direct-acting antiviral (3D) regimen containing ombitasvir, paritaprevir, ritonavir, and dasabuvir with or without ribavirin (RBV) is approved for treatment of hepatitis C virus (HCV) genotype 1 (GT1)/human immunodeficiency virus type 1 (HIV-1) coinfection. Results of a pharmacokinetic substudy of 3D and darunavir are presented. HCV/HIV-1-coinfected subjects were randomized to maintain an antiretroviral regimen with darunavir at 800 mg once daily (QD) or switched to a regimen with darunavir at 600 mg twice daily (BID). On study day 1, subjects received 3D and RBV plus darunavir for 12 weeks. Pharmacokinetic parameters were compared for darunavir and ritonavir with and without 3D (week 4 and day -1). Pharmacokinetic parameters of 3D were compared to historical data. Ten subjects received darunavir QD, and 12 subjects received darunavir BID. The central value ratios (90% confidence interval [CI]) for maximum concentrations (Cmax), area under the plasma concentration-time curve between 0 and 24 h postdose (AUC24), and trough plasma concentration at 24 h postdose (C24) of darunavir administered QD with 3D versus administration of darunavir alone were 0.92 (0.72, 1.18), 0.83 (0.71, 0.98), and 0.64 (0.44, 0.93), respectively. The ratios (90% CI) for darunavir Cmax, AUC12, and C12 administered BID with 3D were 0.92 (0.76, 1.12), 0.88 (0.73, 1.05), and 0.73 (0.58, 0.92), respectively. Exposures of 3D were similar to or slightly lower than those in historical data. All darunavir trough concentrations (Ctrough) associated with an HIV-1 RNA level of >40 copies/ml were above the darunavir 50% effective concentration (EC50) of 550 ng/ml for resistant virus. In conclusion, the 3D regimen with darunavir QD or BID did not affect darunavir Cmax and AUC, whereas the darunavir Ctrough decreased. Changes in pharmacokinetic parameters of 3D were not considered clinically significant. Episodes of intermittent HIV-1 viremia were infrequent and were not associated with darunavir Ctrough values below 550 ng/ml. (This study has been registered at ClinicalTrials.gov under identifier NCT01939197.).

Relationship between venetoclax exposure, rituximab coadministration, and progression-free survival in patients with relapsed or refractory chronic lymphocytic leukemia: demonstration of synergy.

Venetoclax is indicated at a dosage of 400 mg daily (QD) for the treatment of patients with chronic lymphocytic leukemia (CLL) with 17p deletion who have received at least 1 prior therapy. Ongoing trials are evaluating venetoclax in combination with CD20 targeting monoclonal antibodies, such as rituximab. The objective of this research was to characterize the relationship between venetoclax exposures and progression-free survival (PFS) and to evaluate the effect of rituximab coadministration on PFS in patients with relapsed or refractory (R/R) CLL/small lymphocytic lymphoma (SLL). A total of 323 patients from 3 clinical studies of venetoclax, with and without rituximab coadministration, were pooled for the analyses. A time-variant relative risk survival model was used to relate plasma venetoclax concentrations and rituximab administration to PFS. Demographics and baseline disease characteristics were evaluated for their effect on PFS. A concentration-dependent effect of venetoclax on PFS and a prolonged synergistic effect of 6 cycles of concomitant rituximab were identified. The 17p deletion chromosomal aberration was not identified to affect the PFS of patients treated with venetoclax. A venetoclax dose of 400 mg daily QD was estimated to result in a substantial median PFS of 1.8 years (95% confidence interval [CI], 1.7-2.1), whereas the addition of 6 cycles of rituximab was estimated to increase the median PFS to 3.9 years (95% CI, 2.8-5.6). The analysis demonstrates a concentration-dependent effect of venetoclax on PFS and also a synergistic effect with rituximab. Combining venetoclax with the CD20 targeting monoclonal antibody rituximab in R/R CLL/SLL patients provides substantial synergistic benefit compared with increasing the venetoclax monotherapy dose.