The effects of single- and multiple-dose administration of bococizumab (RN316/PF-04950615), a humanized IgG2Δa monoclonal antibody binding proprotein convertase subtilisin/kexin type 9, in hypercholesterolemic subjects treated with and without atorvastatin: Results from four phase I studies.

AIMS: Three single-dose and one multiple-dose phase I studies were conducted in subjects with primary hypercholesterolemia to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of bococizumab, a proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor. METHODS: The dosing schedules for hypercholesterolemic subjects randomized in the four phase I studies were (1) ascending, single, intravenous (IV) bococizumab (0.3, 1, 3, 6, 12, or 18 mg/kg), or placebo (N = 48; baseline low-density lipoprotein cholesterol [LDL-C] ≥130 mg/dL); (2) single, IV bococizumab (0.5 or 4 mg/kg; no placebo) added to ongoing atorvastatin 40 mg/day (N = 24); (3) single, fixed, subcutaneous (SC) bococizumab (100 or 200 mg), or IV bococizumab (200 mg; no placebo; N = 49; baseline LDL-C ≥130 mg/dL); and (4) weekly IV bococizumab (0.25, 0.5, 1, or 1.5 mg/kg) or placebo for 4 weeks (N = 67; baseline LDL-C ≥130 mg/dL). RESULTS: Bococizumab pharmacokinetics were well characterized following single IV or SC doses and following multiple IV doses. Exposure to single-dose bococizumab increased slightly greater than dose-proportionally and clearance decreased with increasing dose. In the single-dose studies, maximal mean percent reductions from baseline in LDL-C ranged from 43% (0.3 mg/kg) to 84% (18 mg/kg) in bococizumab-treated subjects, compared with 2% for placebo. For the multiple-dose study, maximal reductions in LDL-C ranged from 55% (0.25 mg/kg) to 66% (1 mg/kg) in bococizumab-treated subjects, compared with 9% for placebo. In all studies, adverse events were infrequent, transient, and not dose-related. CONCLUSIONS: Bococizumab was generally safe and well tolerated. Bococizumab lowered LDL-C levels substantially in all four studies.

Effects of 12 weeks of treatment with intravenously administered bococizumab, a humanized monoclonal antibody blocking proprotein convertase subtilisin/kexin type 9, in hypercholesterolemic subjects on high-dose statin.

AIMS: Two multiple-dose phase II studies were conducted in subjects with primary hypercholesterolemia to evaluate the LDL-C lowering efficacy, safety, and tolerability of bococizumab, a proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor. METHODS: The results from the two phase II, double-blinded, randomized, placebo-controlled, multicenter studies conducted in the USA and Canada were combined. In Study 1, 90 subjects with LDL-C ≥100 mg/dL received intravenous (IV) placebo or bococizumab 0.25, 1, 3, or 6 mg/kg. In Study 2, 45 subjects with LDL-C ≥80 mg/dL received IV placebo or bococizumab 1 or 3 mg/kg. Subjects were treated every 4 weeks for 12 weeks. Dosing was interrupted if LDL-C dipped to ≤25 mg/dL and resumed if LDL-C returned to ≥40 mg/dL. The primary endpoint was percent LDL-C reduction from baseline at Week 12. RESULTS: At Week 12, the reductions from baseline in LDL-C vs placebo in the bococizumab 0.25, 1, 3, and 6 mg/kg groups were 9.3%, 10.2%, 41.6%, and 52.0%, respectively (P < .001 vs placebo for all). LDL-C reductions were greater (69.9%) in subjects who received all three doses of bococizumab 6 mg/kg (P < .001 vs placebo). Pharmacogenomic analysis revealed that 15% of hyperlipidemic subjects carried polymorphisms associated with familial hypercholesterolemia, with maximal LDL-C reductions being similar between carriers and noncarriers. Adverse events were mild, unrelated to bococizumab, and resolved by Week 12. CONCLUSIONS: These studies demonstrated that bococizumab safely and effectively lowered LDL-C in hypercholesterolemic subjects on high doses of statin.

Molecular target modulation, imaging, and clinical evaluation of gastrointestinal stromal tumor patients treated with sunitinib malate after imatinib failure.

PURPOSE: To evaluate sunitinib activity and potential cellular and molecular correlates in gastrointestinal stromal tumor (GIST) patients after imatinib failure, in addition to assessing the safety and pharmacokinetics (PK) of different dose schedules. EXPERIMENTAL DESIGN: In this open-label, dose-ranging, phase I/II study, 97 patients with metastatic imatinib-resistant/intolerant GIST received sunitinib at doses of 25, 50, or 75 mg/d on one of three schedules. Serial tumor imaging was done using computed tomography and [18F]fluoro-2-deoxy-d-glucose positron emission tomography scanning. PK and cell proliferation and KIT phosphorylation status in tumor biopsies were also analyzed. RESULTS: Clinical benefit was observed in 52 patients (54%: 7 objective partial responses, 45 stable disease > or =6 months). Decreased tumor glycolytic activity was shown in most patients within 7 days of starting sunitinib using [18F]fluoro-2-deoxy-d-glucose positron emission tomography. Sunitinib treatment was associated with reduced tumor cell proliferation by >25% in 52% of cases analyzed and reduced levels of phospho-KIT in tumor biopsies (indicating target modulation). The recommended dose schedule was 50 mg/d for 4 weeks followed by 2 weeks off treatment. On the 50-mg dose across all schedules, 79% of PK-evaluable patients achieved total drug trough concentrations above the target concentration (50 ng/mL) within 14 days of dosing. In addition, adverse events were generally mild to moderate in severity. CONCLUSION: Cellular and molecular analyses showed that sunitinib clinical activity is associated with inhibition of KIT in GIST following imatinib failure, illustrating the rational approach used to develop a therapy aimed at the underlying oncogenic signaling pathway aberrancy.

Circulating levels of soluble KIT serve as a biomarker for clinical outcome in gastrointestinal stromal tumor patients receiving sunitinib following imatinib failure.

PURPOSE: To evaluate changes in circulating levels of soluble KIT (sKIT) extracellular domain as a potential biomarker for clinical outcome in gastrointestinal stromal tumor patients treated with the multitargeted tyrosine kinase inhibitor sunitinib following imatinib failure in a previously reported phase III study. EXPERIMENTAL DESIGN: Patients received sunitinib 50 mg/d (n = 243) or placebo (n = 118) daily in 6-week cycles (4 weeks on, 2 weeks off treatment). Plasma sKIT levels were sampled every 2 weeks in cycle 1 and on days 1 and 28 of subsequent cycles; analyzed by ELISA; and evaluated using Prentice criteria, Cox proportional hazards models, and proportion of treatment effect (PTE) analysis. RESULTS: From 4 weeks on treatment and onward, significant differences were shown between treatment groups (P < 0.0001) in sKIT level changes from baseline (median levels decreased with sunitinib and increased with placebo). Decreases in sKIT levels were a significant predictor of longer time to tumor progression (TTP). Patients with reduced levels at the end of cycle 2 had a median TTP of 34.3 weeks versus 16.0 weeks for patients with increased levels [hazard ratio, 0.71; 95% confidence interval (95% CI), 0.61-0.83; P < 0.0001], and changes in sKIT levels replaced treatment as a stronger predictor of TTP (PTE, 0.80; 95% CI, 0.34-3.70), showing even greater surrogacy on cycle 3 day 1 (PTE, 0.98; 95% CI, 0.39-3.40). CONCLUSIONS: The results suggest that circulating plasma sKIT levels seem to function as a surrogate marker for TTP in gastrointestinal stromal tumor patients. Additional studies are warranted to confirm and expand these findings.

Primary and secondary kinase genotypes correlate with the biological and clinical activity of sunitinib in imatinib-resistant gastrointestinal stromal tumor.

PURPOSE: Most gastrointestinal stromal tumors (GISTs) harbor mutant KIT or platelet-derived growth factor receptor alpha (PDGFRA) kinases, which are imatinib targets. Sunitinib, which targets KIT, PDGFRs, and several other kinases, has demonstrated efficacy in patients with GIST after they experience imatinib failure. We evaluated the impact of primary and secondary kinase genotype on sunitinib activity. PATIENTS AND METHODS: Tumor responses were assessed radiologically in a phase I/II trial of sunitinib in 97 patients with metastatic, imatinib-resistant/intolerant GIST. KIT/PDGFRA mutational status was determined for 78 patients by using tumor specimens obtained before and after prior imatinib therapy. Kinase mutants were biochemically profiled for sunitinib and imatinib sensitivity. RESULTS: Clinical benefit (partial response or stable disease for > or = 6 months) with sunitinib was observed for the three most common primary GIST genotypes: KIT exon 9 (58%), KIT exon 11 (34%), and wild-type KIT/PDGFRA (56%). Progression-free survival (PFS) was significantly longer for patients with primary KIT exon 9 mutations (P = .0005) or with a wild-type genotype (P = .0356) than for those with KIT exon 11 mutations. The same pattern was observed for overall survival (OS). PFS and OS were longer for patients with secondary KIT exon 13 or 14 mutations (which involve the KIT-adenosine triphosphate binding pocket) than for those with exon 17 or 18 mutations (which involve the KIT activation loop). Biochemical profiling studies confirmed the clinical results. CONCLUSION: The clinical activity of sunitinib after imatinib failure is significantly influenced by both primary and secondary mutations in the predominant pathogenic kinases, which has implications for optimization of the treatment of patients with GIST.

Prognostic nomogram for sunitinib in patients with metastatic renal cell carcinoma.

BACKGROUND: In a randomized, phase 3 trial, sunitinib demonstrated superior efficacy over interferon-alfa as first-line therapy in patients with metastatic clear-cell renal cell carcinoma (RCC). On the basis of outcome data from that trial, the authors developed a nomogram for predicting the probability of 12-month progression-free survival for patients who received sunitinib therapy. METHODS: Three-hundred seventy-five patients who received sunitinib in the phase 3 trial were the subject of the current analysis. Nomogram pretreatment predictor variables included corrected serum calcium levels, the number of metastatic sites, hemoglobin levels, prior nephrectomy, the presence of lung and liver metastases, thrombocytosis, Eastern Cooperative Oncology Group performance status, time from diagnosis to treatment, and serum levels of alkaline phosphatase and lactate dehydrogenase. Investigator-assessed progression-free survival was the predicted outcome endpoint. Internal validation of the nomogram consisted of quantification of the discrimination with the concordance index and assessment of calibration. RESULTS: One-hundred seventy-four of 375 patients (46%) who received sunitinib achieved an objective response, and the median progression-free survival was 10.8 months (95% confidence interval, 10.6-12.6 months). A nomogram for predicting the probability of 12-month progression-free survival for patients who received sunitinib therapy was constructed on the basis of a Cox regression model from 11 parameters that were determined before treatment. The concordance index was 0.633. CONCLUSIONS: A nomogram was developed from pretreatment clinical features to predict the probability of achieving 12-month progression-free survival with sunitinib therapy for metastatic clear-cell RCC. The authors concluded that independent validation of the nomogram and additional studies to identify tumor-specific prognostic factors are warranted.

Activity of sunitinib in patients with advanced neuroendocrine tumors.

PURPOSE: Standard cytotoxic chemotherapy has limited efficacy in metastatic neuroendocrine tumor patients. Neuroendocrine tumors express vascular endothelial growth factor (VEGF) and its receptor (VEGFR). Sunitinib malate, an oral tyrosine kinase inhibitor, has activity against VEGFRs as well as platelet-derived growth factor receptors, stem-cell factor receptor, glial cell line-derived neurotrophic factor, and FMS-like tyrosine kinase-3. We evaluated the efficacy of sunitinib in a two-cohort, phase II study of advanced carcinoid and pancreatic neuroendocrine tumor patients. PATIENTS AND METHODS: Patients were treated with repeated 6-week cycles of oral sunitinib (50 mg/d for 4 weeks, followed by 2 weeks off treatment). Patients were observed for response, survival, and adverse events. Patient-reported outcomes were assessed. RESULTS: Among 109 enrolled patients, 107 received sunitinib (carcinoid, n = 41; pancreatic endocrine tumor, n = 66). Overall objective response rate (ORR) in pancreatic endocrine tumor patients was 16.7% (11 of 66 patients), and 68% (45 of 66 patients) had stable disease (SD). Among carcinoid patients, ORR was 2.4% (one of 41 patients), and 83% (34 of 41 patients) had SD. Median time to tumor progression was 7.7 months in pancreatic neuroendocrine tumor patients and 10.2 months in carcinoid patients. One-year survival rate was 81.1% in pancreatic neuroendocrine tumor patients and 83.4% in carcinoid patients. No significant differences from baseline in patient-reported quality of life or fatigue were observed during treatment. CONCLUSION: Sunitinib has antitumor activity in pancreatic neuroendocrine tumors; its activity against carcinoid tumors could not be definitively determined in this nonrandomized study. Randomized trials of sunitinib in patients with neuroendocrine tumors are warranted.

Phase II study of sunitinib malate, an oral multitargeted tyrosine kinase inhibitor, in patients with metastatic breast cancer previously treated with an anthracycline and a taxane.

PURPOSE: Sunitinib is an oral, multitargeted tyrosine kinase inhibitor that inhibits vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor, stem cell factor receptor (KIT), and colony-stimulating factor-1 receptor. This phase II, open-label, multicenter study evaluated sunitinib monotherapy in patients with metastatic breast cancer (MBC). PATIENTS AND METHODS: Sixty-four patients previously treated with an anthracycline and a taxane received sunitinib 50 mg/d in 6-week cycles (4 weeks on, then 2 weeks off treatment). The primary end point was objective response rate. Plasma samples were obtained for pharmacokinetic and biomarker analysis. RESULTS: Seven patients achieved a partial response (median duration, 19 weeks), giving an overall response rate of 11%. Three additional patients (5%) maintained stable disease for >or= 6 months. Median time to progression and overall survival were 10 and 38 weeks, respectively. Notably, responses occurred in triple negative tumors and HER2-positive, trastuzumab-treated patients. Thirty-three patients (52%) required dose interruption during >or= 1 cycle, and 25 patients required dose reduction (39%). Thirty-six patients (56%) had dose modifications due to adverse events (AEs). Treatment was associated with increases in plasma VEGF and decreases in soluble VEGFRs and KIT. The most common AEs were fatigue, nausea, diarrhea, mucosal inflammation, and anorexia. Most AEs were mild to moderate (grade 1 to 2) in severity and were effectively managed with dose delays or reductions. CONCLUSION: Sunitinib is active in patients with heavily pretreated MBC. Most AEs were of mild-to-moderate severity and manageable with supportive treatment and/or dose modification. Further studies in breast cancer are warranted.

Circulating protein biomarkers of pharmacodynamic activity of sunitinib in patients with metastatic renal cell carcinoma: modulation of VEGF and VEGF-related proteins.

BACKGROUND: Sunitinib malate (SUTENT) is an oral, multitargeted tyrosine kinase inhibitor, approved multinationally for the treatment of advanced RCC and of imatinib-resistant or - intolerant GIST. The purpose of this study was to explore potential biomarkers of sunitinib pharmacological activity via serial assessment of plasma levels of four soluble proteins from patients in a phase II study of advanced RCC: VEGF, soluble VEGFR-2 (sVEGFR-2), placenta growth factor (PlGF), and a novel soluble variant of VEGFR-3 (sVEGFR-3). METHODS: Sunitinib was administered at 50 mg/day on a 4/2 schedule (4 weeks on treatment, 2 weeks off treatment) to 63 patients with metastatic RCC after failure of first-line cytokine therapy. Predose plasma samples were collected on days 1 and 28 of each cycle and analyzed via ELISA. RESULTS: At the end of cycle 1, VEGF and PlGF levels increased >3-fold (relative to baseline) in 24/54 (44%) and 22/55 (40%) cases, respectively (P < 0.001). sVEGFR-2 levels decreased >or= 30% in 50/55 (91%) cases and >or= 20% in all cases (P < 0.001) during cycle 1, while sVEGFR-3 levels were decreased >or= 30% in 48 of 55 cases (87%), and >or= 20% in all but 2 cases. These levels tended to return to near-baseline after 2 weeks off treatment, indicating that these effects were dependent on drug exposure. Overall, significantly larger changes in VEGF, sVEGFR-2, and sVEGFR-3 levels were observed in patients exhibiting objective tumor response compared with those exhibiting stable disease or disease progression (P < 0.05 for each analyte; analysis not done for PlGF). CONCLUSION: Sunitinib treatment in advanced RCC patients leads to modulation of plasma levels of circulating proteins involved in VEGF signaling, including soluble forms of two VEGF receptors. This panel of proteins may be of value as biomarkers of the pharmacological and clinical activity of sunitinib in RCC, and of angiogenic processes in cancer and other diseases.

Sunitinib versus interferon alfa in metastatic renal-cell carcinoma.

BACKGROUND: Since sunitinib malate has shown activity in two uncontrolled studies in patients with metastatic renal-cell carcinoma, a comparison of the drug with interferon alfa in a phase 3 trial is warranted. METHODS: We enrolled 750 patients with previously untreated, metastatic renal-cell carcinoma in a multicenter, randomized, phase 3 trial to receive either repeated 6-week cycles of sunitinib (at a dose of 50 mg given orally once daily for 4 weeks, followed by 2 weeks without treatment) or interferon alfa (at a dose of 9 MU given subcutaneously three times weekly). The primary end point was progression-free survival. Secondary end points included the objective response rate, overall survival, patient-reported outcomes, and safety. RESULTS: The median progression-free survival was significantly longer in the sunitinib group (11 months) than in the interferon alfa group (5 months), corresponding to a hazard ratio of 0.42 (95% confidence interval, 0.32 to 0.54; P<0.001). Sunitinib was also associated with a higher objective response rate than was interferon alfa (31% vs. 6%, P<0.001). The proportion of patients with grade 3 or 4 treatment-related fatigue was significantly higher in the group treated with interferon alfa, whereas diarrhea was more frequent in the sunitinib group (P<0.05). Patients in the sunitinib group reported a significantly better quality of life than did patients in the interferon alfa group (P<0.001). CONCLUSIONS: Progression-free survival was longer and response rates were higher in patients with metastatic renal-cell cancer who received sunitinib than in those receiving interferon alfa (ClinicalTrials.gov numbers, NCT00098657 and NCT00083889 [ClinicalTrials.gov]).

Efficacy and safety of sunitinib in patients with advanced gastrointestinal stromal tumour after failure of imatinib: a randomised controlled trial.

BACKGROUND: No effective therapeutic options for patients with unresectable imatinib-resistant gastrointestinal stromal tumour are available. We did a randomised, double-blind, placebo-controlled, multicentre, international trial to assess tolerability and anticancer efficacy of sunitinib, a multitargeted tyrosine kinase inhibitor, in patients with advanced gastrointestinal stromal tumour who were resistant to or intolerant of previous treatment with imatinib. METHODS: Blinded sunitinib or placebo was given orally once daily at a 50-mg starting dose in 6-week cycles with 4 weeks on and 2 weeks off treatment. The primary endpoint was time to tumour progression. Intention-to-treat, modified intention-to-treat, and per-protocol analyses were done. This study is registered at ClinicalTrials.gov, number NCT00075218. FINDINGS: 312 patients were randomised in a 2:1 ratio to receive sunitinib (n=207) or placebo (n=105); the trial was unblinded early when a planned interim analysis showed significantly longer time to tumour progression with sunitinib. Median time to tumour progression was 27.3 weeks (95% CI 16.0-32.1) in patients receiving sunitinib and 6.4 weeks (4.4-10.0) in those on placebo (hazard ratio 0.33; p<0.0001). Therapy was reasonably well tolerated; the most common treatment-related adverse events were fatigue, diarrhoea, skin discolouration, and nausea. INTERPRETATION: We noted significant clinical benefit, including disease control and superior survival, with sunitinib compared with placebo in patients with advanced gastrointestinal stromal tumour after failure and discontinuation of imatinab. Tolerability was acceptable.

Sunitinib in patients with metastatic renal cell carcinoma.

CONTEXT: Current treatment options for metastatic renal cell carcinoma (RCC) are limited and there is a need to identify novel and effective therapies. Sunitinib malate is an oral multitargeted tyrosine kinase inhibitor, which has shown activity in an initial study of cytokine-refractory metastatic RCC patients. OBJECTIVE: To confirm the antitumor efficacy of sunitinib as second-line treatment in patients with metastatic clear-cell RCC, the predominant cell type of this malignancy. DESIGN, SETTING, AND PATIENTS: Open-label, single-arm, multicenter clinical trial. Patients were enrolled between February and November 2004, with follow-up continuing until disease progression, unacceptable toxicity, or withdrawal of consent. The reported data apply through August 2005. Patients (N = 106) had metastatic clear-cell RCC, which had progressed despite previous cytokine therapy. INTERVENTION: Repeated 6-week cycles of sunitinib, 50 mg per day given orally for 4 consecutive weeks followed by 2 weeks off per treatment cycle. MAIN OUTCOME MEASURES: Assessment of clinical response, degree of tumor regression on imaging studies using the Response Evaluation Criteria in Solid Tumors (RECIST) guidelines. Primary end point was overall objective response rate (complete plus partial). Secondary end points were progression-free survival and safety. Response was evaluated by independent third-party core imaging laboratory and by treating physicians (investigator assessment). RESULTS: All 106 patients received sunitinib and were included in the intent-to-treat population for safety analyses. Of these, 105 patients were evaluable for efficacy analyses. The objective response rate according to an independent third-party assessment resulted in 36 patients with partial response (34%; 95% confidence interval, 25%-44%), and a median progression-free survival of 8.3 months (95% confidence interval, 7.8-14.5 months). The most common adverse events experienced by patients were fatigue in 30 (28%) and diarrhea 21 (20%). Neutropenia, elevation of lipase, and anemia were the most common laboratory abnormalities observed in 45 (42%), 30 (28%), and 27 (26%) patients, respectively. CONCLUSION: The results of this trial demonstrate the efficacy and manageable adverse-event profile of sunitinib as a single agent in second-line therapy for patients with cytokine-refractory metastatic clear-cell RCC. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00077974.

Activity of SU11248, a multitargeted inhibitor of vascular endothelial growth factor receptor and platelet-derived growth factor receptor, in patients with metastatic renal cell carcinoma.

PURPOSE: Renal cell carcinoma (RCC) is characterized by loss of von Hippel Lindau tumor suppressor gene activity, resulting in high expression of pro-angiogenic growth factors: vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF). SU11248 (sunitinib malate), a small molecule inhibitor with high binding affinity for VEGF and PDGF receptors, was tested for clinical activity in patients with metastatic RCC. PATIENTS AND METHODS: Patients with metastatic RCC and progression on first-line cytokine therapy were enrolled onto a multicenter phase II trial. SU11248 monotherapy was administered in repeated 6-week cycles of daily oral therapy for 4 weeks, followed by 2 weeks off. Overall response rate was the primary end point, and time to progression and safety were secondary end points. Results Twenty-five (40%) of 63 patients treated with SU11248 achieved partial responses; 17 additional patients (27%) demonstrated stable disease lasting > or = 3 months. Median time to progression in the 63 patients was 8.7 months. Dosing was generally tolerated with manageable toxicities. CONCLUSION: SU11248, a multitargeted receptor tyrosine kinase inhibitor of VEGF and PDGF receptors, demonstrates antitumor activity in metastatic RCC as second-line therapy, a setting where no effective systemic therapy is presently recognized. The genetics of RCC and these promising clinical results support the hypothesis that VEGF and PDGF receptor-mediated signaling is an effective therapeutic target in RCC.

Sch-66336 (sarasar) and other benzocycloheptapyridyl farnesyl protein transferase inhibitors: discovery, biology and clinical observations.

Farnesyl Protein Transferase as a target for therapeutic intervention is currently under investigation in human clinical trials. Sch-66336 (sarasar), a benzocycloheptapyridyl Farnesyl Transferase Inhibitor (FTI), has been found to be effective in cellular proliferation assays and in in vivo oncology models both as a single agent and in combination with other anti-cancer agents. Clinically, early evidence is being generated that suggests efficacy in humans, particularly in patients with leukemia. Herein, we review the biology of FPT, the discovery of Sch-66336 and other benzocycloheptapyridyl FTIs, and the clinical evaluation of Sch-66336 for the treatment of leukemia and solid tumors.

Mobilization of dendritic cells in cancer patients treated with granulocyte colony-stimulating factor and chemotherapy.

The number of dendritic cells (DC) circulating in the peripheral blood of cancer patients were monitored at multiple time points during chemotherapy and granulocyte colony-stimulating factor (G-CSF) support. DC were identified via the lack of expression of standard lineage markers and high expression of HLA-DR (LN-/DR+). The expression of DC-associated markers, including CD83, CD11c, IL-3Ralpha (CDw123) and CD86, within this LN-/DR+ population was also monitored. Maximal mobilization occurred during recovery on d 12, with a mean 32-fold increase in LN-/DR+ numbers. The most striking increase was observed in the LN-/DR+/CD83+ cell population: 12 d after commencement of treatment, the proportion of these cells had increased by approximately 120-fold when compared with baseline. Peripheral blood mononuclear cell (PBMC) and CD34+ cell numbers also peaked 12 d into the treatment regimen in most patients. These data suggest that it should be possible to acquire substantial numbers of DC from leukapheresis products collected from cancer patients undergoing a standard treatment regimen of chemotherapy and G-CSF. This strategy may be a feasible, low-risk means of acquiring cells for DC-based vaccine studies.