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PDF - 1128K, Figure S1. Knockdown of CDK7 and CDK9 can inhibit RNAP II CTD P-Ser2 and P-Ser5. Figure S2. LY2857785 and flavopiridol inhibit MCL-1, XIAP protein expression and induce CASP-3 and cleaved PARP in AML cell MV-4-11. Table S1. LY2857785 inhibits solid tumor cell proliferation and induces apoptosis. Table S2. 261 probsets gene signature in sens and res cell lines. Table S3. LY2857785 inhibits proliferation of normal human hematopoietic cells in vitro.

XLSX - 54K, Table S2. 261 probsets gene signature in sens and res cell lines in Excel format.

DNA-dependent RNA polymerase II (RNAP II) largest subunit RPB1 C-terminal domain (CTD) kinases, including CDK9, are serine/threonine kinases known to regulate transcriptional initiation and elongation by phosphorylating Ser 2, 5, and 7 residues on CTD. Given the reported dysregulation of these kinases in some cancers, we asked whether inhibiting CDK9 may induce stress response and preferentially kill tumor cells. Herein, we describe a potent CDK9 inhibitor, LY2857785, that significantly reduces RNAP II CTD phosphorylation and dramatically decreases MCL1 protein levels to result in apoptosis in a variety of leukemia and solid tumor cell lines. This molecule inhibits the growth of a broad panel of cancer cell lines, and is particularly efficacious in leukemia cells, including orthotopic leukemia preclinical models as well as in ex vivo acute myeloid leukemia and chronic lymphocytic leukemia patient tumor samples. Thus, inhibition of CDK9 may represent an interesting approach as a cancer therapeutic target, especially in hematologic malignancies. Mol Cancer Ther; 13(6); 1442–56. ©2014 AACR.

Supplementary Table 1. Summary of 33 Patients Treated with Abemaciclib in Dose Escalation. Supplementary Table 2. Baseline patient and disease characteristics. Supplementary Table 3. Possibly related treatment-emergent adverse events (>10% all grades) for hormone receptorpositive breast cancer cohort (n=19) receiving combination therapy with abemaciclib plus fulvestrant. Supplementary Table 4. Summary of abemaciclib pharmacokinetic parameters following a single oral administration. Supplementary Table 5. Summary of abemaciclib pharmacokinetic parameters following repeated once-daily (Q24H) or twice-daily (Q12H) oral administration. Supplementary Table 6. Efficacy for NSCLC cohort, overall and by KRAS status. Supplementary Table 7. Efficacy for other tumor-specific cohorts.

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Percentage Change from Baseline (PCB) for B-cells (CD19+) and Immunoglobulins (Ig)at 20-day time intervals post-baseline.

Percentage Change from Baseline (PCB) for B-cells (CD19+) and Immunoglobulins (Ig)at 20-day time intervals post-baseline.

PDF file - 247KB, Model simulations of the plasma concentration, the biomarker levels of p-Rb, TopoIIalpha and pHH3, and the effect parameters driving tumor growth inhibition for a 21 day daily dosing regimen of 25 (red line), 50 (blue line) and 100 mg/kg (green line) LY2835219 using the mean parameter estimates.

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Bortezomib pharmacokinetic parameters following a single intravenous 1.3 mg/m2 bolus dose and varying single intravenous doses of tabalumab

PDF file - 122KB, Supplementary Table 1. Summary of available PK and biomarker data. Supplementary Table 2. Definitions of PK, biomarker and tumor model parameters.

Purpose: AME-133v is a humanized monoclonal antibody engineered to have increased affinity to CD20 and mediate antibody-dependent cell-mediated cytotoxicity (ADCC) better than rituximab. Safety, pharmacokinetics, and efficacy were assessed in a phase 1/2 trial in patients with previously treated follicular lymphoma (FL).Patients and Methods: AME-133v was characterized in vitro by ADCC and cell binding assays. A phase 1 study was conducted in which 23 previously treated patients with FL were assigned sequentially to one of five dose-escalation cohorts of AME-133v at 2, 7.5, 30, 100, or 375 mg/m2 weekly × 4 doses.Results: AME-133v showed a 13- to 20-fold greater binding affinity for CD20 and was 5- to 7-fold more potent than rituximab in ADCC assays. Cell binding assays showed AME-133v and rituximab competed for an overlapping epitope on the CD20 antigen, and AME-133v inhibited binding of biotinylated rituximab to CD20 in a concentration-dependent manner. AME-133v was well tolerated by patients and common related adverse events included chills and fatigue. One patient experienced a dose-limiting toxicity of neutropenia. AME-133v showed nonlinear pharmocokinetics with properties similar to rituximab. Selective reduction of B cells during and after AME-133v treatment was shown by flow cytometry of peripheral blood. A partial or complete response was observed in 5 of 23 (22%) patients and the median progression-free survival was 25.4 weeks.Conclusions: AME-133v was safe and well tolerated at the doses tested. AME-133v showed encouraging results as an anti-CD20 therapy in heavily pretreated FL patients with the less favorable FcγRIIIa F-carrier genotype. Clin Cancer Res; 18(5); 1395–403. ©2012 AACR.

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Bortezomib pharmacokinetic parameters following a single intravenous 1.3 mg/m2 bolus dose in the presence or absence of tabalumab and dexamethasone

Purpose: Tabalumab, a human mAb that neutralizes B-cell–activating factor (BAFF), demonstrated antitumor activity in xenograft models of multiple myeloma. Here we report on a phase I study of relapsed/refractory multiple myeloma patients in which the primary objective was to identify a tolerable and potentially efficacious dose of tabalumab when combined with bortezomib.Experimental Design: Forty-eight patients were enrolled; 20 to the dose-escalation cohort, and 28 to cohort expansion in which a dose of 100 mg of tabalumab was evaluated. All patients had received either prior bortezomib or an immunomodulatory drug; the median number of prior therapies was 3. Bortezomib was administered intravenously on days 1, 4, 8, and 11 of a 21-day schedule. Tabalumab was given every 21 days for 3 cycles, then every 42 days thereafter.Results: The most common grade 3/4 toxicities included thrombocytopenia, neutropenia, pneumonia, and peripheral sensory neuropathy. There were no dose-limiting toxicities, and the maximum tolerated dose was not reached. Pharmacokinetic data suggested serum exposure increased in a greater than dose-proportional manner up to a dose of 100 mg. Out of 46 evaluable patients, 20 had confirmed responses. The median time to progression (9 patients censored) was 4.8 months, and the median response duration (4 patients censored) was 7.2 months.Conclusions: A dose of 100 mg tabalumab in combination with bortezomib was well tolerated and active and is currently under further investigation. Clin Cancer Res; 22(23); 5688–95. ©2016 AACR.

PDF file - 350KB, Model simulations of tumor size dynamics for 17 days of growth followed by a 21-day daily dosing regimen of 25, 50 and 100 mg/kg of LY2835219 for the full model (green line) or for the model incorporating tumor growth inhibition by cell cycle arrest alone (blue line), compared to control tumor growth (red line).

Purpose: Selective inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) represents a promising therapeutic strategy. However, despite documented evidence of clinical activity, limited information is available on the optimal dosing strategy of CDK4/6 inhibitors. Here, we present an integrated semi-mechanistic pharmacokinetic/pharmacodynamic model to characterize the quantitative pharmacology of LY2835219, a CDK4/6 inhibitor, in xenograft tumors.Experimental Design: LY2835219 plasma concentrations were connected to CDK4/6 inhibition and cell-cycle arrest in colo-205 human colorectal xenografts by incorporating the biomarkers, phospho-(ser780)-Rb, topoisomerase II α, and phosphohistone H3, into a precursor-dependent transit compartment model. This biomarker model was then connected to tumor growth inhibition (TGI) by: (i) relating the rate of tumor growth to mitotic cell density, and (ii) incorporating a concentration-dependent mixed cytostatic/cytotoxic effect driving quiescence and cell death at high doses. Model validation was evaluated by predicting LY2835219-mediated antitumor effect in A375 human melanoma xenografts.Results: The model successfully described LY2835219-mediated CDK4/6 inhibition, cell-cycle arrest, and TGI in colo-205, and was validated in A375. The model also demonstrated that a chronic dosing strategy achieving minimum steady-state trough plasma concentrations of 200 ng/mL is required to maintain durable cell-cycle arrest. Quiescence and cell death can be induced by further increasing LY2835219 plasma concentrations.Conclusions: Our model provides mechanistic insight into the quantitative pharmacology of LY2835219 and supports the therapeutic dose and chronic dosing strategy currently adopted in clinical studies. Clin Cancer Res; 20(14); 3763–74. ©2014 AACR.

Pharmacokinetic parameters of tabalumab in multiple myeloma patients

PDF file - 22KB, Model simulated dose response curve for the average (red line), minimum (green line) and maximum (blue line) levels of p-Rb and pHH3 over a 24 period at steady state following daily dosing.

PDF file - 76KB, External validation of the biomarker model by VPC with data collected in colo-205 following daily oral dosing of 50 mg/kg of LY2835219 for 56 days or two cycles of 50 mg/kg for 21 days with a 7 day rest period.

PDF file - 71KB, VPC of the biomarker model in colo-205 xenograft bearing mice following a single 3.125, 6.25 or 12.5 mg/kg oral dose of LY2835219.

PDF file - 349KB, External validation of the PK model by VPC in colo-205 xenograft bearing mice receiving a single 6.25, 12.5, 25 and 50 mg/kg oral dose of LY2835219, or with oral doses of 50 and 100 mg/kg administered daily for 21 days.

In non-small cell lung cancer (NSCLC), platelet-derived growth factor receptor (PDGFR) mediates angiogenesis, tissue invasion, and tumor interstitial pressure. Olaratumab (IMC-3G3) is a fully human anti-PDGFRα monoclonal antibody. This Phase II study assessed safety and efficacy of olaratumab+paclitaxel/carboplatin (P/C) versus P/C alone for previously untreated advanced NSCLC.Patients received up to six 21-day cycles of P 200mg/m131 patients were: 67 with olaratumab+P/C and 64 with P/C; 74% had nonsquamous NSCLC. Median PFS was similar between olaratumab+P/C and P/C (4.4 months each) (HR 1.29; 95% CI [0.86-1.93]; p=0.21). Median OS was similar between olaratumab+P/C (11.8 months) and P/C (11.5 months) (HR 1.04; 95% CI [0.68-1.57]; p=0.87). Both arms had similar toxicity profiles. All evaluable cases were PDGFR-negative by immunohistochemistry. Tumor stroma PDGFR expression was evaluable in 23/131 patients, of which 78% were positive.The addition of olaratumab to P/C did not result in significant prolongation of PFS or OS in advanced NSCLC. Olaratumab studies in other patient populations, including soft tissue sarcoma (NCT02783599), pancreatic cancer (NCT03086369), and pediatric malignancies (NCT02677116) are underway.

Background and Objectives Olaratumab is a recombinant human monoclonal antibody that binds to platelet-derived growth factor receptor-α (PDGFRα). In a randomized phase II study, olaratumab plus doxorubicin met its predefined primary endpoint for progression-free survival and achieved a highly significant improvement in overall survival versus doxorubicin alone in patients with advanced or metastatic soft tissue sarcoma (STS). In this study, we characterize the pharmacokinetics (PKs) of olaratumab in a cancer patient population. Methods Olaratumab was tested at 15 or 20 mg/kg in four phase II studies (in patients with nonsmall cell lung cancer, glioblastoma multiforme, STS, and gastrointestinal stromal tumors) as a single agent or in combination with chemotherapy. PK sampling was performed to measure olaratumab serum levels. PK data were analyzed by nonlinear mixed-effect modeling techniques using NONMEM®. Results The PKs of olaratumab were best described by a two-compartment PK model with linear clearance (CL). Patient body weight was found to have a significant effect on both CL and central volume of distribution (V 1), whereas tumor size significantly affected CL. A small subset of patients developed treatment-emergent anti-drug antibodies (TE-ADAs); however, TE-ADAs did not have any effect on CL or PK time course of olaratumab. There was no difference in the PKs of olaratumab between patients who received olaratumab as a single agent or in combination with chemotherapy. Conclusion The PKs of olaratumab were best described by a model with linear disposition. Patient body weight and tumor size were found to be significant covariates. The PKs of olaratumab were not affected by immunogenicity or chemotherapeutic agents. Electronic supplementary material The online version of this article (doi:10.1007/s40262-017-0562-0) contains supplementary material, which is available to authorized users.

Summary Background Treatment with doxorubicin is a present standard of care for patients with metastatic soft-tissue sarcoma and median overall survival for those treated is 12–16 months, but few, if any, novel treatments or chemotherapy combinations have been able to improve these poor outcomes. Olaratumab is a human antiplatelet-derived growth factor receptor α monoclonal antibody that has antitumour activity in human sarcoma xenografts. We aimed to assess the efficacy of olaratumab plus doxorubicin in patients with advanced or metastatic soft-tissue sarcoma. Methods We did an open-label phase 1b and randomised phase 2 study of doxorubicin plus olaratumab treatment in patients with unresectable or metastatic soft-tissue sarcoma at 16 clinical sites in the USA. For both the phase 1b and phase 2 parts of the study, eligible patients were aged 18 years or older and had a histologically confirmed diagnosis of locally advanced or metastatic soft-tissue sarcoma not previously treated with an anthracycline, an Eastern Cooperative Oncology Group (ECOG) performance status of 0–2, and available tumour tissue to determine PDGFRα expression by immunohistochemistry. In the phase 2 part of the study, patients were randomly assigned in a 1:1 ratio to receive either olaratumab (15 mg/kg) intravenously on day 1 and day 8 plus doxorubicin (75 mg/m 2 ) or doxorubicin alone (75 mg/m 2 ) on day 1 of each 21-day cycle for up to eight cycles. Randomisation was dynamic and used the minimisation randomisation technique. The phase 1b primary endpoint was safety and the phase 2 primary endpoint was progression-free survival using a two-sided α level of 0·2 and statistical power of 0·8. This study was registered with ClinicalTrials.gov, number NCT01185964. Findings 15 patients were enrolled and treated with olaratumab plus doxorubicin in the phase 1b study, and 133 patients were randomised (66 to olaratumab plus doxorubicin; 67 to doxorubicin alone) in the phase 2 trial, 129 (97%) of whom received at least one dose of study treatment (64 received olaratumab plus doxorubicin, 65 received doxorubicin). Median progression-free survival in phase 2 was 6·6 months (95% CI 4·1–8·3) with olaratumab plus doxorubicin and 4·1 months (2·8–5·4) with doxorubicin (stratified hazard ratio [HR] 0·67; 0·44–1·02, p=0·0615). Median overall survival was 26·5 months (20·9–31·7) with olaratumab plus doxorubicin and 14·7 months (9·2–17·1) with doxorubicin (stratified HR 0·46, 0·30–0·71, p=0·0003). The objective response rate was 18·2% (9·8–29·6) with olaratumab plus doxorubicin and 11·9% (5·3–22·2) with doxorubicin (p=0·3421). Steady state olaratumab serum concentrations were reached during cycle 3 with mean maximum and trough concentrations ranging from 419 μg/mL (geometric coefficient of variation in percentage [CV%] 26·2) to 487 μg/mL (CV% 33·0) and from 123 μg/mL (CV% 31·2) to 156 μg/mL (CV% 38·0), respectively. Adverse events that were more frequent with olaratumab plus doxorubicin versus doxorubicin alone included neutropenia (37 [58%] vs 23 [35%]), mucositis (34 [53%] vs 23 [35%]), nausea (47 [73%] vs 34 [52%]), vomiting (29 [45%] vs 12 [18%]), and diarrhoea (22 [34%] vs 15 [23%]). Febrile neutropenia of grade 3 or higher was similar in both groups (olaratumab plus doxorubicin: eight [13%] of 64 patients vs doxorubicin: nine [14%] of 65 patients). Interpretation This study of olaratumab with doxorubicin in patients with advanced soft-tissue sarcoma met its predefined primary endpoint for progression-free survival and achieved a highly significant improvement of 11·8 months in median overall survival, suggesting a potential shift in the treatment of soft-tissue sarcoma. Funding Eli Lilly and Company.

Purpose Olaratumab is a recombinant human IgG1 monoclonal antibody against PGDFRα. Olaratumab plus doxorubicin improved survivalversus doxorubicin in an open-label, randomised phase 2 soft tissue sarcoma (STS) trial. We characterised the olaratumab exposure–response relationship for progression-free survival (PFS), overall survival (OS), and safety. Methods PFS and OS data from the 133 patients enrolled in the phase 2 study were analysed using time-to-event modelling. The effect of olaratumab on PFS/OS was explored using the trough serum concentration after cycle 1 (Cmin1) and the average concentration throughout treatment (Cavg). The rate of treatment-emergent adverse events (TEAEs) was compared across olaratumab exposure quartiles. Results PFS and OS were described by models with an exponential hazard function and inhibitory EMAX functions to describe the effect of olaratumab, regardless of the PK endpoint. The olaratumab EC50s for PFS (ECmin150 = 82.0 µg/mL, ECavg50 = 179 µg/mL) and OS (ECmin150 = 66.1 µg/mL, ECavg50 = 134 µg/mL) corresponded to the median and 25th percentile of Cmin1/Cavg in the study, respectively. Maximum predicted improvement in the hazard ratio for OS and PFS was approximately 75% and 60%, respectively. There was no change in the rate of TEAEs with increasing olaratumab serum levels. Conclusions PFS/OS benefits occurred without a rate change in TEAEs across quartiles. Maximum benefit in OS was achieved in the upper three quartiles and a potential of early disease progression in the lower quartile of olaratumab serum exposure. These results prompted a loading dose strategy in the ongoing phase 3 STS trial.

Background: Abemaciclib, a small molecule inhibitor with selectivity against cyclin-dependent kinases 4 and 6 (CDK4/6), induces G1 arrest in Rb-proficient human breast cancers. In an early phase clinical trial, the safety and antitumor activity of abemaciclib (LY2835219) were evaluated in 2 cohorts of patients with metastatic breast cancer (mBC). One cohort evaluated single-agent abemaciclib in an unselected population of patients with mBC [Part D], while the combination of abemaciclib plus fulvestrant was evaluated in patients with hormone receptor positive (HR+) mBC [Part G]. We previously reported early results for these 2 cohorts of patients with mBC treated with either single-agent abemaciclib or the combination of abemaciclib plus fulvestrant (Patnaik et al, ASCO 2014). In the single-agent cohort, 47 patients with previously treated mBC were enrolled (36 HR+). All patients with >30% tumor reduction had HR+ mBC (13 of 36 patients). In this group of 13 patients with HR+ mBC, 9 patients had confirmed response for an objective response rate of 25%, and 4 patients had unconfirmed response. This study was ongoing with 14 of 36 HR+ mBC patients on treatment at time of analysis (range 238-471 days). Patients continuing on single-agent abemaciclib included 4 patients with unconfirmed response and 6 patients with confirmed response. For the combination of abemaciclib plus fulvestrant, 18 patients with HR+ mBC enrolled and 13 patients (72%) were still on treatment (range 31-143 days) at the time of analysis. Methods: In the single-agent cohort, patients with mBC were treated with abemaciclib at 150 or 200mg orally every 12 hours on a continuous schedule. In the combination cohort, patients with HR+ mBC (n=18) were treated with the combination of abemaciclib plus fulvestrant. Patients received abemaciclib at 200mg orally every 12 hours on a continuous schedule. Patients also received fulvestrant at 500mg intramuscularly every month. NCI CTCAE v4.0 was used to grade adverse events (AEs) and RECIST v1.1 was used to assess tumor response. Results: In the single-agent cohort, patients began enrolling in May 2012 with the last patient enrolled in March 2013. Patients had a median of 7 prior systemic therapies and 81% of patients had ≥2 metastatic sites. In the combination cohort, patients began enrolling in September 2013 with the last patient enrolled in January 2014. Patients in the combination cohort had a median of 4 prior systemic therapies and 67% of patients had ≥2 metastatic sites. An updated analysis will be presented for objective response rate, duration of treatment and clinical benefit rate and will include an additional 6 months of information for both the single-agent and combination cohorts. New analyses will include time to response, duration of response, change in tumor size over time, and characteristics of responders. In addition, safety data will include longer term follow-up through approximately September 2014. Conclusions: Abemaciclib is an oral cell cycle inhibitor that demonstrates single-agent activity against mBC, especially for HR+ disease. Based on its safety and efficacy profile, abemaciclib warrants further clinical investigation in confirmatory studies, both as a single agent and in combination with endocrine therapy. Citation Format: Sara M Tolaney, Lee S Rosen, Muralidhar Beeram, Jonathan W Goldman, Leena Gandhi, Anthony W Tolcher, Kyriakos P Papadopoulos, Drew W Rasco, Scott P Myrand, Palaniappan Kulanthaivel, Joan M Andrews, Martin Frenzel, Damien M Cronier, Edward M Chan, Keith T Flaherty, Patrick Y Wen, Geoffrey I Shapiro, Amita Patnaik. Clinical activity of abemaciclib, an oral cell cycle inhibitor, in metastatic breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-19-13.

Purpose: Selective inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) represents a promising therapeutic strategy. However, despite documented evidence of clinical activity, limited information is available on the optimal dosing strategy of CDK4/6 inhibitors. Here, we present an integrated semi-mechanistic pharmacokinetic/pharmacodynamic model to characterize the quantitative pharmacology of LY2835219, a CDK4/6 inhibitor, in xenograft tumors. Experimental Design: LY2835219 plasma concentrations were connected to CDK4/6 inhibition and cell-cycle arrest in colo-205 human colorectal xenografts by incorporating the biomarkers, phospho-(ser780)-Rb, topoisomerase II α, and phosphohistone H3, into a precursor-dependent transit compartment model. This biomarker model was then connected to tumor growth inhibition (TGI) by: (i) relating the rate of tumor growth to mitotic cell density, and (ii) incorporating a concentration-dependent mixed cytostatic/cytotoxic effect driving quiescence and cell death at high doses. Model validation was evaluated by predicting LY2835219-mediated antitumor effect in A375 human melanoma xenografts. Results: The model successfully described LY2835219-mediated CDK4/6 inhibition, cell-cycle arrest, and TGI in colo-205, and was validated in A375. The model also demonstrated that a chronic dosing strategy achieving minimum steady-state trough plasma concentrations of 200 ng/mL is required to maintain durable cell-cycle arrest. Quiescence and cell death can be induced by further increasing LY2835219 plasma concentrations. Conclusions: Our model provides mechanistic insight into the quantitative pharmacology of LY2835219 and supports the therapeutic dose and chronic dosing strategy currently adopted in clinical studies. Clin Cancer Res; 20(14); 3763–74. ©2014 AACR.

This phase 2 study assessed the safety and efficacy of ocaratuzumab, a humanized anti-CD20 monoclonal antibody. Fifty patients with previously treated follicular lymphoma (FL) and a low-affinity genotype of FcγRIIIa received ocaratuzumab 375 mg/m(2) weekly for 4 weeks. Grade 3/4/5 adverse events (AEs) were reported in 11/1/1 patients, respectively. Serious AEs were reported by 11/50 patients, and three discontinued due to AEs. One patient died from aspiration pneumonia due to possibly drug-related nausea and vomiting. Investigator-assessed response rate was 30% (15/50), including four complete responses (CR), three CR unconfirmed (CRu) and eight partial responses (PR). Investigator-assessed median Progression-free survivial (PFS) was 38.3 weeks. Ocaratuzumab's pharmacokinetic profile was similar to that reported for rituximab. Lymphocyte subset analysis showed significant, selective reduction of B-cells during and after ocaratuzumab treatment. Ocaratuzumab at this dose and schedule is active and well tolerated in patients with previously treated FL with low affinity FcγRIIIa genotypes. ClinTrials registry number: NCT00354926.

DNA-dependent RNA polymerase II (RNAP II) largest subunit RPB1 C-terminal domain (CTD) kinases, including CDK9, are serine/threonine kinases known to regulate transcriptional initiation and elongation by phosphorylating Ser 2, 5, and 7 residues on CTD. Given the reported dysregulation of these kinases in some cancers, we asked whether inhibiting CDK9 may induce stress response and preferentially kill tumor cells. Herein, we describe a potent CDK9 inhibitor, LY2857785, that significantly reduces RNAP II CTD phosphorylation and dramatically decreases MCL1 protein levels to result in apoptosis in a variety of leukemia and solid tumor cell lines. This molecule inhibits the growth of a broad panel of cancer cell lines, and is particularly efficacious in leukemia cells, including orthotopic leukemia preclinical models as well as in ex vivo acute myeloid leukemia and chronic lymphocytic leukemia patient tumor samples. Thus, inhibition of CDK9 may represent an interesting approach as a cancer therapeutic target, especially in hematologic malignancies. Mol Cancer Ther; 13(6); 1442–56. ©2014 AACR.

Summary In this double-blind, Phase 2 study, 220 patients with relapsed/refractory multiple myeloma were randomly assigned 1:1:1 to receive placebo (N = 72), tabalumab 100 mg (N = 74), or tabalumab 300 mg (N = 74), each in combination with dexamethasone 20 mg and subcutaneous bortezomib 1·3 mg/m2 on a 21-day cycle. No significant intergroup differences were observed among primary (median progression-free survival [mPFS]) or secondary efficacy outcomes. The mPFS was 6·6, 7·5 and 7·6 months for the tabalumab 100, 300 mg and placebo groups, respectively (tabalumab 100 mg vs. placebo Hazard ratio (HR) [95% confidence interval (CI)] = 1·13 [0·80–1·59], P = 0·480; tabalumab 300 mg vs. placebo HR [95% CI] = 1·03 [0·72–1·45], P = 0·884). The most commonly-reported treatment-emergent adverse events were thrombocytopenia (37%), fatigue (37%), diarrhoea (35%) and constipation (32%). Across treatments, patients with low baseline BAFF (also termed TNFSF13B) expression (n = 162) had significantly longer mPFS than those with high BAFF expression (n = 55), using the 75th percentile cut-off point (mPFS [95% CI] = 8·3 [7·0–9·3] months vs. 5·8 [3·7–6·6] months; HR [95% CI] = 1·59 [1·11–2·29], P = 0·015). Although generally well tolerated, PFS was not improved during treatment with tabalumab compared to placebo. A higher dose of 300 mg tabalumab did not improve efficacy compared to the 100 mg dose. Nonetheless, BAFF appears to have some prognostic value in patients with multiple myeloma.

Purpose: Tabalumab, a human mAb that neutralizes B-cell–activating factor (BAFF), demonstrated antitumor activity in xenograft models of multiple myeloma. Here we report on a phase I study of relapsed/refractory multiple myeloma patients in which the primary objective was to identify a tolerable and potentially efficacious dose of tabalumab when combined with bortezomib. Experimental Design: Forty-eight patients were enrolled; 20 to the dose-escalation cohort, and 28 to cohort expansion in which a dose of 100 mg of tabalumab was evaluated. All patients had received either prior bortezomib or an immunomodulatory drug; the median number of prior therapies was 3. Bortezomib was administered intravenously on days 1, 4, 8, and 11 of a 21-day schedule. Tabalumab was given every 21 days for 3 cycles, then every 42 days thereafter. Results: The most common grade 3/4 toxicities included thrombocytopenia, neutropenia, pneumonia, and peripheral sensory neuropathy. There were no dose-limiting toxicities, and the maximum tolerated dose was not reached. Pharmacokinetic data suggested serum exposure increased in a greater than dose-proportional manner up to a dose of 100 mg. Out of 46 evaluable patients, 20 had confirmed responses. The median time to progression (9 patients censored) was 4.8 months, and the median response duration (4 patients censored) was 7.2 months. Conclusions: A dose of 100 mg tabalumab in combination with bortezomib was well tolerated and active and is currently under further investigation. Clin Cancer Res; 22(23); 5688–95. ©2016 AACR.

11542Background: Olaratumab (O) is an antibody against platelet-derived growth factor receptor alpha. In a randomized phase 2 study, O in combination with doxorubicin (dox) demonstrated a significa...

TPS524 Background: Olaratumab is a human IgG1 monoclonal antibody that specifically binds human platelet-derived growth factor receptor (PDGFR)-α and blocks PDGF-mediated signaling pathways. Increased PDGFRα expression is observed in pancreatic cancer tissue, and has been suggested to play a role in the mesenchymal transition of pancreatic cancer. An ongoing trial designed to evaluate the safety and efficacy of olaratumab in combination with nab-paclitaxel/gemcitabine (nPG) in patients with unresectable metastatic pancreatic cancer not previously treated for metastatic disease is currently being conducted. Methods: JGDP (NCT03086369) is a global Phase 1b/Phase 2 study being conducted to evaluate the safety and efficacy of olaratumab in combination with nPG as first-line therapy in patients with Stage IV pancreatic cancer (ECOG PS ≤1). In the Phase 1b portion of the study, patients will receive intravenous (iv) olaratumab following a 3+3 dose escalation scheme at two different schedules: on Days 1, 8 and 15 at doses of 15 mg/kg and 20 mg/kg, or on Days 1 and 15 at 20 mg/kg and 25 mg/kg. Olaratumab will be given in combination with nPG (125 mg/m2 iv/1000 mg/m2 iv) on Days 1, 8, and 15 of a 28-day cycle. After the maximum tolerated dose has been identified, additional patients will be enrolled in a cohort expansion to confirm the safety of the combination prior to proceeding to the Phase 2 portion of the study. In the Phase 2 study, approximately 162 patients will be randomized at a 1:1 ratio to receive olaratumab at the recommended Phase 2 dose regimen or placebo, both in combination with nPG (125 mg/m2 iv/1000 mg/m2 iv). Treatment will continue until disease progression or other discontinuation criteria are met. The primary end point of the Phase 2 study is overall survival; a 2-sided α level of 0.20 will be applied. Assuming OS HR = 0.67, there is ≥80% power to show a significant difference in OS between study arms. Secondary end points include progression free survival, duration of response, objective response rate, patient-reported outcomes, and safety. As of September 2017, enrollment for the Phase 1b study is currently ongoing. Clinical trial information: NCT03086369.

Olaratumab (Olara), a fully human monoclonal antibody that selectively binds human platelet-derived growth factor receptor alpha and blocks ligand binding, shows encouraging efficacy in combination with Dox in STS. Patients with metastatic or locally advanced STS not amenable to treatment with surgery or curative radiotherapy, aged ?18 years with an ECOG PS of 0-2 and documented LVE fraction ?50% were included. The primary objective was to assess the effect of Olara on the PK of Dox. Secondary objectives were to further characterize the PK and safety profiles of Olara alone and in combination with Dox. Drug-drug interaction (DDI) was assessed in 21-day cycles, where patients received each drug alone (Cycle 1) then in combination (Cycle 2). In Cycles 3-8, patients with clinical benefit could continue treatment with Olara+Dox. 15-mg/kg Olara was given IV over ∼60 min; 75-mg/m2 Dox was given IV over ∼15 min. Overall, 25 patients (10 male and 15 female, aged 27-83 years) received at least one dose of study drug; as planned, 15 patients were evaluable for PK and DDI assessment. The AUC and Cmax for Dox were similar with or without Olara; the 90% CIs for the ratios of geometric LS means for AUC were within the standard no-effect boundary (0.8, 1.25); the 90% CI for Cmax was only slightly out of the boundary but with a Cmax ratio close to unity (0.984). After the first infusion of Olara alone (Cycle 1, Day 10), a mean Olara Cmax of 293μg/mL was achieved at ∼2h post start of infusion, with a mean t1/2 of ∼157h. The mean Olara CL was 0.0259L/h. After the second infusion (Cycle 2, Day 1, Olara+Dox), Olara serum concentration had a median tmax of ∼2.8h post start of infusion, and the mean Cmax was higher (393μg/mL), due to the residual Olara serum concentrations from cycle 1. The mean t1/2 (∼131h) and CL (0.0218L/h) were, however, similar to those obtained after the first infusion. These Olara PK results are consistent with those previously reported. No deaths occurred. The most common treatment-emergent AE reported during the study were nausea (48%) and fatigue (44%). One Grade 4 IRR was observed; there was no evidence of QT prolongation. IV infusion of Olara did not have a clinically relevant effect on systemic exposure to Dox when both agents were given in combination. The PK of Olara alone and with Dox was consistent with previously reported data. Olara+Dox had an acceptable safety profile Citation Format: Victor Villalobos, Mark Agulnik, Seth M. Pollack, Daniel A. Rushing, Arun Singh, Brian A. Van Tine, Chukwuemeka Okereke, Wee Teck Ng, Damien M. Cronier. A phase I open-label study to evaluate the effect of olaratumab on the pharmacokinetics (PK) of doxorubicin (Dox) in patients with advanced soft tissue sarcoma (STS). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT145.

Purpose: AME-133v is a humanized monoclonal antibody engineered to have increased affinity to CD20 and mediate antibody-dependent cell-mediated cytotoxicity (ADCC) better than rituximab. Safety, pharmacokinetics, and efficacy were assessed in a phase 1/2 trial in patients with previously treated follicular lymphoma (FL). Patients and Methods: AME-133v was characterized in vitro by ADCC and cell binding assays. A phase 1 study was conducted in which 23 previously treated patients with FL were assigned sequentially to one of five dose-escalation cohorts of AME-133v at 2, 7.5, 30, 100, or 375 mg/m2 weekly × 4 doses. Results: AME-133v showed a 13- to 20-fold greater binding affinity for CD20 and was 5- to 7-fold more potent than rituximab in ADCC assays. Cell binding assays showed AME-133v and rituximab competed for an overlapping epitope on the CD20 antigen, and AME-133v inhibited binding of biotinylated rituximab to CD20 in a concentration-dependent manner. AME-133v was well tolerated by patients and common related adverse events included chills and fatigue. One patient experienced a dose-limiting toxicity of neutropenia. AME-133v showed nonlinear pharmocokinetics with properties similar to rituximab. Selective reduction of B cells during and after AME-133v treatment was shown by flow cytometry of peripheral blood. A partial or complete response was observed in 5 of 23 (22%) patients and the median progression-free survival was 25.4 weeks. Conclusions: AME-133v was safe and well tolerated at the doses tested. AME-133v showed encouraging results as an anti-CD20 therapy in heavily pretreated FL patients with the less favorable FcγRIIIa F-carrier genotype. Clin Cancer Res; 18(5); 1395–403. ©2012 AACR.

Background: Mantle cell lymphoma (MCL) is characterized by a recurrent chromosomal translocation t(11;14) that leads to aberrant expression of Cyclin D1 which, together with cyclin dependent kinases 4 and 6 (CDK4/6), inhibits the retinoblastoma (Rb) tumor suppressor protein and thereby induces malignant proliferation. Abemaciclib, a cell cycle inhibitor selective for CDK4/6 (Gelbert et al, 2014), has shown single agent clinical activity against multiple human tumors including lung cancer and breast cancer (Shapiro et al, ASCO 2013; Goldman et al, ASCO 2014; Patnaik et al, ASCO 2014). Based on molecular pathogenesis and single agent activity in preclinical models of human MCL, abemaciclib was evaluated in a single arm Phase II study for patients with relapsed or refractory MCL. Methods: The primary objective of this study was to estimate the disease control rate, which includes response (complete + unconfirmed complete + partial) plus stable disease, for patients who received abemaciclib for relapsed or refractory mantle cell lymphoma (MCL). Patients were scheduled to receive abemaciclib (200 mg) orally every 12 hours on Days 1 through 28 of each 28-day cycle. Eligibility criteria permitted an unlimited number of prior systemic therapies including high dose chemotherapy with stem cell transplantation, Eastern Cooperative Oncology Group (ECOG) performance status = 1.5 x 109/L, and platelets >= 75 x 109/L. National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) v4.0 were used to grade adverse events. Response Criteria for Non-Hodgkin’s Lymphomas (Cheson et al, 1999) were used to assess clinical activity. Plasma samples for pharmacokinetics were performed both after a single oral dose and after multiple doses at steady state. Flow cytometry was used to isolate circulating MCL cells for evaluation of pharmacodynamic effect on Rb phosphorylation. Results: In this Phase II study, 22 patients with relapsed or refractory MCL received single agent oral treatment with abemaciclib. Among these patients, 91% presented at initial diagnosis with Stage III or IV disease. At the time of study entry, these patients (9 female and 13 male) had a median age of 66 years (range: 53-83), 59% had ECOG performance status of 1 or 2, and all patients had constitutional B symptoms. Eighteen patients received >= 2 prior systemic therapies, and previous treatments for the overall study population included not only high dose chemotherapy with stem cell transplantation but also rituximab (96%), cyclophosphamide-based therapy (86%), cytarabine-based therapy (64%), temsirolimus (55%), and bendamustine (41%). Patients received 1-16 cycles of treatment with abemaciclib and 8 of 22 patients (36%) completed >= 6 cycles. The most common possibly related treatment-emergent adverse events across all grades included diarrhea (55%, including 9% G3/4), nausea (23%, with no G3/4), vomiting (32%, with no G3/4), fatigue (18%, with no G3/4), thrombocytopenia (55%, including 32% G3/4), neutropenia (36%, including 32% G3/4), and anemia (18%, with no G3/4). Plasma concentrations of abemaciclib were comparable to those previously observed and associated with clinical activity in patients with advanced non-hematologic malignancies. For patients with at least one post-treatment radiographic evaluation, preliminary investigator assessment indicates that single agent therapy with abemaciclib was associated with stable disease for 9 patients and partial response for 5 patients, including durable disease control (>= 6 cycles) in 8 of these 14 patients with relapsed or refractory MCL. Conclusions: Abemaciclib, a cell cycle inhibitor, demonstrates evidence of durable disease control as a single agent for patients with relapsed or refractory MCL. Disclosures Hahka-Kemppinen: Eli Lilly and Company: Employment, Equity Ownership. Xiaohui Wang:Eli Lilly and Company: Employment. Brueck:Eli Lilly and Company: Employment. Caldwell:Eli Lilly and Company: Employment. Beckmann:Eli Lilly and Company: Employment, Equity Ownership. Gelbert:Eli Lilly and Company : Consultancy. Cronier:Eli Lilly and Company: Employment. Lin:Eli Lilly and Company: Employment. Li:Eli Lilly and Company: Employment. Chan:Eli Lilly and Company: Employment, Equity Ownership. Pfreundschuh:Amgen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Boerhinger Ingelheim: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; Spectrum: Research Funding.

LY2835219 is a novel cell cycle inhibitor selective for the cyclin-dependent kinases CDK4 and CDK6 (CDK4/6), which act in a protein complex with D-type cyclins to enable G1 to S cell cycle progression. Preclinical models indicate this complex plays a critical role in breast cancer. We conducted a phase I study with expansion cohorts to evaluate the safety, pharmacokinetics, and antitumor activity of LY2835219 in 5 different tumor types: glioblastoma; melanoma; and cancers of the lung, colon/rectum and breast. In the expansion cohorts, LY2835219 was administered continuously at 150-200mg orally every 12 hours on Days 1-28 of a 28-day cycle. RECIST v1.1 was used to assess tumor response. The most common possibly related treatment-emergent adverse events across the expansion cohorts (n=132) included diarrhea (5% G3/4), nausea (3% G3/4), fatigue (2% G3/4), vomiting (2% G3/4) and neutropenia (11% G3/4). In the metastatic breast cancer (MBC) cohort, 47 patients with a median of 7 prior systemic regimens received therapy with LY2835219. Across all MBC patients, 9 achieved a best overall response of confirmed partial response (PR), 24 achieved stable disease (SD), 11 had progressive disease (PD), and 3 were not evaluable for response. Among the 36 HR+ patients, there were 9 confirmed partial responses for an ORR of 25%. In addition, 20 of these 36 HR+ patients (56%) had SD: 7 patients had SD < 24 weeks and 13 patients (including 2 patients with unconfirmed PR) had SD ≥ 24 weeks. The disease control rate (DCR = CR + PR + SD) was 70% for all patients and 81% for HR+ patients. The median PFS was 5.8 months for all patients and 9.1 months for HR+ patients, with 18 HR+ patients (including the 2 unconfirmed PRs) still on LY2835219 therapy (range: 2.8-15.5 months). In conclusion, LY2835219 demonstrates evidence of durable single-agent activity for women with MBC after multiple prior systemic regimens for metastatic disease, particularly for those women with HR+ tumors, and merits further clinical investigation in MBC. Citation Format: Amita Patnaik, Lee S. Rosen, Sara M. Tolaney, Anthony W. Tolcher, Jonathan W. Goldman, Leena Gandhi, Kyriakos P. Papadopoulos, Muralidhar Beeram, Drew W. Rasco, Scott P. Myrand, Palaniappan Kulanthaivel, Lily Li, Martin Frenzel, Damien M. Cronier, Edward M. Chan, Keith T. Flaherty, Patrick Y. Wen, Geoffrey I. Shapiro. Clinical activity of LY2835219, a novel cell cycle inhibitor selective for CDK4 and CDK6, in patients with metastatic breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT232. doi:10.1158/1538-7445.AM2014-CT232

8026 Background: LY2835219, a novel cell cycle inhibitor selective for the cyclin-dependent kinases CDK4 and CDK6 (CDK4/6), has shown antitumor activity in human NSCLC xenograft models. Importantly...

534 Background: Cyclin-dependent kinases 4 and 6 (CDK4/6) act with D-type cyclins to enable cell proliferation. LY2835219, a small molecule inhibitor of CDK4/6, has shown antitumor activity in xeno...

2500 Background: Cyclin dependent kinases 4 and 6 (CDK4/6) act with D-type cyclins to inactivate the retinoblastoma (Rb) tumor suppressor protein and enable cell cycle progression from G1 to S phase. LY2835219 is a selective inhibitor of CDK4/6 that shows antitumor activity in preclinical models of human cancer and also distributes efficiently to the brain. We performed a phase 1 study to evaluate safety, pharmacokinetics, pharmacodynamics, and antitumor activity of LY2835219. Methods: 3+3 dose escalation was followed by expansions in 5 tumor types (brain metastases permitted): non-small cell lung cancer (NSCLC), glioblastoma, breast cancer, melanoma, and colorectal cancer. LY2835219 was taken orally every 12 or 24 hours (in escalation) and every 12 hours (in expansions) on days 1-28 of a 28-day cycle. Results: 55 patients (pts) received LY2835219. In escalation, 33 pts received LY2835219 on 1 of 2 schedules: 50, 100, 150, 225 mg every 24 hours (Q24H) or 75, 100, 150, 200, 275 mg every 12 hours (Q12H). On the Q24H schedule, the maximum tolerated dose (MTD) was not identified. On the Q12H schedule, the MTD was 200mg Q12H with dose limiting toxicity of G3 fatigue at 200 mg (1/6 evaluable pts) and 275 mg (2/3 evaluable pts). At 200mg Q12H, the mean Cmax and AUC0-24hr at steady state were 285 ng/mL and 5502 ng-hr/ml, respectively. In skin, LY2835219 induced pharmacodynamic inhibition of both Rb phosphorylation and topoisomerase IIα expression. In the ongoing expansions, 22 pts have received LY2835219. Across the study, the most common related adverse events were diarrhea (52%, including 5% G3), nausea (30%, 4% G3), fatigue (21%, 7% G3), vomiting (18%, 2% G3), and neutropenia (16%, 7% G3). 15 pts have reached ≥4 cycles for stable disease or better with 3 pts achieving 8, 16, and 26 cycles. One pt with ovarian cancer had a durable CA-125 response with >50% decrease for 16 cycles. One pt with KRAS mutant NSCLC had a 27% decrease by RECIST. One pt with CDKN2A-/- NRAS mutant melanoma had a confirmed partial response. Early clinical activity has been observed in ovarian cancer, NSCLC, breast cancer, and melanoma. Conclusions: LY2835219 shows acceptable safety and early clinical activity as a single agent for patients with advanced cancer. Clinical trial information: NCT01394016.

Abstract 447 Background: Tabalumab, a human mAb that neutralizes membrane-bound and soluble B cell activating factor (BAFF), has demonstrated both anti-myeloma activity and osteoclastogenesis inhibition in xenograft models of multiple myeloma (MM). We initially conducted a Phase 1 study with the combination of tabalumab and bortezomib in previously-treated MM patients who were not refractory to bortezomib. The results from the dose escalation (Part A) have been previously reported, where a tabalumab dose of 100 mg was selected based on several factors, most notably the stabilization of the peak to trough concentration ratio. The cohort expansion (Part B) has since completed enrollment, and we now report the preliminary results for the entire study. Methods: The primary objective was to identify a safe and potentially efficacious dose of tabalumab to be combined with bortezomib. Bortezomib was given in a standard biweekly fashion, 1.3 mg/m2 IV on days 1, 4, 8, and 11 of a 21 day cycle, and tabalumab at 1, 10, 30, 100, or 300 mg (Part A) or 100 mg (Part B) IV (30 min) on day 1 in Cycles 1 – 3, 5, and 7. The study was later amended to include dexamethasone to assess safety, and 12 patients received dexamethasone in combination with bortezomib and tabalumab. Response was assessed per IMWG criteria and adverse events per CTCAE v3.0. Pharmacokinetic (PK) and pharmacodynamic (PD) samples were obtained throughout the study, including BAFF, IL-1beta, IL-6, IL-10, VEGF, and TNF-alpha. Results: Forty-eight patients were enrolled to the study; 20 to dose escalation (Part A) and 28 to cohort expansion (Part B). The median age was 65.7 years and 56% were women. The median number of prior therapies was 3 (range 1–10). All patients received either bortezomib or an IMiD; 75% received prior bortezomib and 88% received prior IMiD therapy. The median number of cycles was 5.5 (range 1–28). Grade 3/4 toxicities occurring in two or more patients included peripheral sensory neuropathy, pneumonia, thrombocytopenia, neutropenia, diarrhea, musculoskeletal pain, renal failure acute, fatigue, anemia, neuralgia, and gastrointestinal hemorrhage. Most patients discontinued treatment due to progressive disease or adverse events (neuropathy, neuralgia, fatigue, and thrombocytopenia). Two patients died during study participation - one during treatment from acute respiratory distress syndrome and another during follow-up from multiple myeloma. Confirmed responses included 2 complete responses, 4 very good partial responses, and 16 partial responses. Response associated with lower baseline serum BAFF or IL-6 levels, independent of the tabalumab dose. Also, response in patients treated with tabalumab 100 mg appeared to associate with lower baseline serum levels of IL-10 and undetectable TNF-alpha. With 14 patients censored, the TTP was 4.9 months (95% CI: 4 – 8). With 6 patients censored, the median response duration was 7.3 months (95% CI: 3.5 – 13.9). Conclusions: A 100 mg dose of tabalumab in combination with bortezomib was well tolerated; 22 patients achieved a PR or better despite prior bortezomib and/or IMiD therapy. Response correlated with lower baseline serum BAFF levels, supporting the hypothesis that a higher dose of tabalumab should be evaluated. A three-arm study randomizing patients to the combination(s) of bortezomib, dexamethasone, and tabalumab 100 mg vs. tabalumab 300mg vs. placebo is currently enrolling. Disclosures: Raje: Onyx: Consultancy; Celgene: Consultancy; Millennium: Consultancy; Acetylon: Research Funding; Amgen: Research Funding; Eli-Lilly: Research Funding. Richardson:Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees. Schiller:Eli Lilly & Company: Research Funding. Cohen:Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Onyx: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Carpenter:Eli Lilly & Company: Employment. Cronier:Eli Lilly and Company: Employment. Kaiser:Eli Lilly and Company: Employment. Wooldridge:Eli Lilly and Company: Employment. Anderson:Acetylon, Oncopep: Scientific Founder, Scientific Founder Other; Celgene, Millennium, BMS, Onyx: Membership on an entity's Board of Directors or advisory committees.

Dysregulation of the cell cycle, which normally regulates cell proliferation in response to mitogenic signaling and other extracellular stimuli, is a hallmark of cancer. The G1 restriction point is a primary mechanism controlling cell cycle progression and is controlled by the CDK4/6 pathway (CDK4/6-cyclin D1-Rb-CDKN2). The importance of this pathway is highlighted by inactivation of restriction point control in a majority of human tumors. Transition through the restriction point requires phosphorylation of Rb by CDK4/6, and these kinases are considered highly validated cancer drug targets. We have identified and characterized a potent and selective dual CDK4/6 inhibitor, LY2835219. Preclinical characterization was performed with the monomesylate salt (LY2835219-MsOH), which inhibits these kinases with a IC50 of 2 and 10 nM for CDK4 and CDK6, respectively. In vitro, LY2835219-MsOH is a potent inhibitor of Rb phosphorylation resulting in a G1 arrest, and its activity is specific for tumors that have functional Rb protein. In a multiplexed in vivo target inhibition assay (IVTI), LY2835219-MsOH is a potent inhibitor of Rb phosphorylation and induces complete cell cycle arrest 24 hrs after a single dose. In tumor-bearing mice, oral administration of LY2835219-MsOH inhibits tumor growth in a dose-dependent manner in colon (colo-205), glioblastoma (U87MG), acute myeloid leukemia (MV4–11), mantle cell lymphoma (Jeko-1), and lung (H460) xenografts. LY2835219-MsOH may be administered up to 56 days without adverse events or tumor outgrowth. LY2835219-MsOH enhances the in vivo activity of cytotoxic drugs, suggesting that this novel CDK4/6 inhibitor can be used in combination with these anti-neoplastic agents. In summary, we have identified an oral small molecule inhibitor of CDK4/6 that may provide therapeutic benefit to cancer patients with tumors that have functional Rb protein. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B233.

8012 Background: LY2127399 (LY) is a human mAb that neutralizes membrane-bound and soluble B cell activating factor (BAFF). LY has activity in xenograft models of multiple myeloma (MM) and is being...

Since the early 1960s, drug combination therapy has been used to treat cancer, because of the limited number of malignancies that could respond to single-agent chemotherapy. Combination chemotherapy regimens have been designed on the basis of mechanism of action of the drugs, tumor cell specificity, balance between effectiveness and toxicity, and synergy between drugs. But when multiple drugs, combination schedules, sequences and doses are considered, the number of possibilities increases combinatorically, and can not be realistically tested either clinically or in animal models. We have developed a “Virtual Tumor” model to aid with the design of optimal drug schedules. The model combines disparate data, at the cell and tumor level, into a consistent picture, and leverages them to make testable predictions about tumor response. Thousands of simulations can be performed if necessary to find the best treatment regime. We present here a validation study of our Virtual Tumor. We predicted xenograft growth of two anti-cancer drug combinations using experimental data collected from single drug exposure uniquely. We accurately predicted the xenograft course for two different regimens – one simultaneous and one sequential – of the two drugs, which were compared with experimental results in a single-blind test. We show how a computational approach helps explain how multiple drug exposure and correct sequence leads to synergy, and how it can be used to subsequently design optimal schedule and combination treatments. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4918. doi:10.1158/1538-7445.AM2011-4918

Abstract 3942 Background: Pts with FL in whom position 158 on the FcγRIIIa (CD16) gene is heterozygous for valine/phenylalanine (V/F) or homozygous for phenylalanine (F/F) (F-carriers) have natural killer cells with lower binding affinity to IgG than valine homozygote (V/V) pts. These pts showed a lower response rate and shorter time to progression compared with V/V genotype pts after initial rituximab treatment. A humanized IgG1 anti-CD20 monoclonal antibody, LY2469298, was optimized through protein engineering in the Fc region to increase affinity with FcγIIIa and is expected to increase effector function in F-carriers. This phase I study was conducted to evaluate the safety, clinical activity, and pharmacokinetics (PK) of LY2469298 in Japanese pts with relapsed or refractory FL. Methods: Japanese pts with FL who relapsed or progressed after prior treatment, but not within 120 days of prior rituximab, received four infusions of LY2469298 at weekly intervals. The dose was assessed for safety, tolerability, and immunogenicity (HAHA) in 2 cohorts of 100 and 375 mg/m2. Dose-limiting toxicity (DLT) was evaluated from the day of the first infusion until two weeks after the last infusion. Response was evaluated according to the International Workshop Response Criteria (IWRC) at 9 and 21 weeks after the last dose. The PK of LY2469298 were assessed after the first and fourth dose by means of a non-compartmental analysis. Results: Ten pts (male/female: 5/5), median age 60.4 yrs (range: 39–75), were enrolled and treated in 2 cohorts: 3 pts at 100 mg/m2 and 7 pts at 375 mg/m2. The number of pts with stage I/II/III/IV at enrollment was 1/4/1/4, respectively. All pts received 1 or more treatment of prior rituximab alone or rituximab-containing regimen; 3/10 pts were refractory to the regimen. The median number of prior regimens was 2 (range: 1–9). Follicular Lymphoma International Prognostic Index (FLIPI) identified 4 pts at low risk, 2 at intermediate risk, and 4 at high risk. There was one V/V patient in the 375 mg/m2 cohort; all other pts were F-carriers. No DLT was observed in either cohort; therefore, the recommended phase II dose was determined to be 375 mg/m2. The most common adverse events (≥40% of pts) included hematological toxicities and infusion-related reactions: lymphopenia (n=10), pyrexia (8), leukopenia (7), chills (7), and neutropenia (5). Grade 3 or 4 hematological toxicities were lymphopenia (n=7) and neutropenia (2; no G-CSF required). There were no grade 3 or 4 infusion-related reactions; most reactions were limited to the first infusion. B-cell (CD19+) depletion in peripheral blood was rapid and sustained in all pts. B-cell recovery began in the 21-week observation period. LY2469298 was eliminated in a biphasic manner from pts' blood with a elimination half-life of 10 to 14 days. Clearance, elimination half-life, and volume of distribution were similar between the 2 doses. AUC and Cmax increased with dose. Of 10 evaluable pts, responses were observed in 5 pts (3 CR, 1 CRu, and 1 PR). Conclusions: Weekly doses of LY2469298 at 100 and 375 mg/m2 were well tolerated and resulted in evidence of clinical activity in pts with relapsed or refractory FL after prior rituximab alone or rituximab-containing regimens, although 9 of 10 pts were F-carriers. The PK characteristics of clearance, elimination half-life, and volume of distribution of the 2 LY2469298 doses were similar, both of which were eliminated in a biphasic manner. The promising results of this phase I study warrant further investigation of LY2469298 in pts with FL. Disclosures: Off Label Use: LY2469298 is an investigational agent. Matsue:Eli Lilly Japan KK: Employment. Cronier:Lilly UK: Employment. Wooldridge:Eli Lilly & Company: Employment. Koshiji:Eli Lilly Japan KK: Employment.

Background: Single-agent rituximab therapy in patients with follicular lymphoma (FL) who have a low-affinity FcγRIIIa (158-FF or VF; F-carriers) is associated with a lower response rate (RR) and time to progression compared to patients with the high affinity genotype (158-VV). Through protein engineering, the humanized monoclonal antibody (mAb) AME-133v was optimized to achieve a 13-20-fold greater affinity for CD20, ~ 6-fold greater potency at mediating ADCC, and ~ 50% lower complement dependent cytotoxicity compared to rituximab in vitro. Methods: An open-label, multicenter, Phase 1/2 dose-escalation (3+3) study of AME-133v was initiated in patients with relapsed/refractory FL who were confirmed to be FcγRIIIa 158-F-carriers. Eligible patients were treated with four weekly infusions of AME-133v. The objectives of the study are to determine the safety and tolerability, PK profile, objective response rate, and duration of response. The Phase 1 portion is complete and is the subject of this report. Results: Twenty-three patients were enrolled and 22 (12M/10F; median age 61.5) received AME-133v IV once weekly for 4 doses at 2 (n = 3), 7.5 (n = 3), 30 (n = 4), 100 (n = 6) or 375 mg/m2 (n = 6). All treated patients were confirmed to be FcγRIIIa F-carriers (158-VF =12 and 158-FF =10). Patients treated on the trial received a median of 1 prior treatment regimen (range 0-4); 20/21 patients received prior treatment with rituximab and 18/21 patients had prior chemotherapy. Available safety data (n=20) revealed that 18/20 (90%) patients experienced transient adverse events (AEs) on the day of first infusion that were predominantly CTCAE Grades 1 (17/20, 85%) or 2 (6/20, 30%). One patient had transient Grade 3 bronchospasm responsive to standard care. AEs were reported on the day of subsequent infusions in 6 (30%), 2 (10%), and 4 patients (20%) for the 2nd, 3rd, and 4th infusions, respectively, and all were ≤ Grade 2. Neutropenia (n=1) at the 100 mg/m2 dose level was the only SAE reported by an investigator as related to AME-133v, and this event was the only DLT reported. Thus, the MTD was not established during dose escalation. Lymphocyte subset analysis showed that CD19+ B-cells were selectively decreased during and after treatment with AME-133v. The pharmacokinetic (PK) assessment of AME-133v is ongoing. Response data is available for 16 patients at dose levels 2-100 mg/m2. Investigator-assessed CR or PR (Cheson criteria) at 9 weeks was reported in 4/16 patients (25%) in the 2 (1/3), 30 (1/3), and 100 (2/6) mg/m2 cohorts. Conclusions: AME-133v is well tolerated at the doses tested, and the MTD was not established. B-cell depletion and clinical responses were observed in the phase 1 study portion. Accrual continues in Phase 2. Further safety, pharmacodynamic, and response data will become available and will be updated in the final abstract.