Experienced Tumor Regression Research Articles

Abstract 2825: Identification of CDK4/6-response biomarkers using estrogen receptor-positive breast cancer patient-derived xenografts (PDX)

Abstract Endocrine resistance is a clinical challenge for the treatment of estrogen receptor positive (ER+) breast cancer (BC). CDK4/6 blockade in combination with endocrine therapy has shown clinical activity in metastatic ER+ BC refractory to anti-hormonal treatment. However, there is a need for biomarkers that can predict the response to this treatment and improve patient stratification. We aimed to address this issue using xenograft models established from samples of ER+ BC patients. Six ER+ PDXs were treated with continuous doses of a CDK4/6 inhibitor (LEE011, 75mg/kg, 6IW) and a PI3K-alpha inhibitor (BYL719, 35mg/kg, 6IW) as single agents and in combination, and intrinsic sensitivity to these agents was evaluated. The models were then genomically characterized using a capture-based sequencing panel and by digital PCR. One PDX model was intrinsically sensitive to single-agent CDK4/6 inhibition and experienced tumor regression, but all individual tumors eventually escaped therapy after 50 days of treatment. This particular model harbored an ESR1-mutation and concomitant losses of CDKN2A/B. At relapse, we identified the acquisition of an RB1 frameshift mutation. Interestingly, upfront combined treatment with a PI3K-alpha inhibitor delayed the onset of tumor progression. Two out of the remaining five CDK4/6-resistant PDXs harbored either a frameshift mutation in RB1 (plus loss of heterozygosity) or had low pRb protein expression. Two other resistant models harbored CCND1 and MYC amplifications. The remaining one harbored a TSC1 loss. In all the CDK4/6-resistant PDX, however, the combination of CDK4/6 and PI3K-alpha inhibition resulted in tumor regression. From our results, we conclude that loss of G1-cell cycle checkpoint control, such as mutation/loss of RB1 and CCND1-amplification, is associated with lack of response to CDK4/6 blockade in ER+ BC PDX. The addition of a PI3K-alpha inhibitor results in improvement of disease control in all experimental models tested. Citation Format: Violeta Serra, Marta Palafox, Maria-Teresa Herrera, Martin A Rivas, Marta Guzmán, Olga Rodriguez, Judit Grueso, Meritxell Bellet, Mafalda Oliveira, Cristina Saura, Emmanuelle di Tomaso, Giordi Camponigro, Nicholas C. Turner, Javier Cortés, José Baselga. Identification of CDK4/6-response biomarkers using estrogen receptor-positive breast cancer patient-derived xenografts (PDX). [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 2825.

Abstract 2478: A mAb with in vivo therapeutic activity against spontaneous breast tumors in FVB-neuN mice recognizes SLP-2

Abstract BCSC (breast cancer stem cells) derived from FVB-neuN mice bearing primary breast tumors were used to vaccinate mice and vaccine-draining lymph node T cells were adoptively transferred to mice with advanced primary tumors. Treated mice experienced tumor regression and importantly a concomitant serologic response was induced to an antigen that is expressed by BCSC even in Neu-antigen loss tumor cells. We generated a specific mAb (mAb2) reactive against a membrane antigen on BCSC tumorsphere cultures derived from NeuN spontaneous breast tumors but not the counterpart adherent cultures. In vivo administration of mAb2 inhibited progression of macroscopic primary tumors in Her-2/neu transgenic mice. We further observed that the molecule bound by mAb2 is expressed on proliferating but not growth-arrested C2D1-tumorspheres and this antigen is re-expressed when cells are digested into single cell suspension and re-fed with fresh medium. Similar results are observed with 4T1-tumorsphere cells, an additional breast cancer cell line arising initially in BALB/c mice. Interestingly, the target of mAb2 is also down-regulated following irradiation-induced growth arrest of tumor cells. To identify the antigen recognized by mAb2, cultured C2D1-tumorsphere or 4T1-tumorspheres were cells were lysed and the supernatant was immunoprecipitated with mAb2. The proteins captured by mAb2 were separated by 10% SDS-PAGE and visualized by silver staining. The bands of interest were excised then subjected to liquid chromatography-mass spectrometric (LC-MS/MS) analysis. A ∼40 KDa protein was detected in all five experiments from either C2D1-tumorsphere or 4T1-tumorsphere cells. Stomatin-like protein 2 (SLP-2) a 38.5 KDa protein was consistently identified whereas 14 other proteins were sporadically found. Western blots of mAb2 immunoprecipitates from C2D1 or 4T1-tumorsphere lysates were probed with two distinct commercial antibodies against SLP-2 and we confirmed its presence. To validate SLP-2 as the target, an expression vector was transfected into NIH 3T3 cells and FACS analysis demonstrated 19% positive cells versus 3.6% for un-transfected 3T3 cells. SLP-2 overexpression is associated with tumor metastasis and poor prognosis in several types of human tumors. Our results indicate that the antigen recognized by this auto-antibody might have immunodiagnostic or immunotherapeutic potential. Citation Format: Li-Xin Wang, Michael Berk, Gregory E. Plautz. A mAb with in vivo therapeutic activity against spontaneous breast tumors in FVB-neuN mice recognizes SLP-2. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2478. doi:10.1158/1538-7445.AM2015-2478

Abstract 2592: Anti-tumor activity of icotinib (BPI-2009H) and BPI-403B in the BxPC-3 pancreatic cancer cell line

Abstract Introduction: The purpose of this research was to investigate the anti-tumor effect of BPI-2009H and BPI-403B, an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) in the human pancreatic cancer cell lines BxPC-3 and Panc-1, in vitro and in vivo and determine the maximum tolerated dose (MTD) of the compound in mouse. Experimental Design: In vitro, human pancreatic cancer cell lines, BxPC-3 and Panc-1 were exposed to varying concentrations of BPI-2009H and BPI-403B, the concentration of compound required to inhibit growth by fifty percent (IC50) was estimated. In vivo, tumor growth inhibition of low dose BPI-2009H was tested in xenografted nude mice with BxPC-3 pancreatic cancer tumors. The maximum tolerated dose (MTD) was established via oral administration of low, mid and high doses to Harlan mice of both BPI-2009H and BPI-403B. Upon determination of the MTD, the in vivo efficacy of high dose BPI-2009H was evaluated via tumor growth inhibition study on xenografted nude mice with BxPC-3 pancreatic cancer tumors. Results: BPI-2009H, as a single agent, inhibited the growth of BxPC-3 cells in a dose dependent manner, with a relative IC50 value of 25.8 μM. BPI-403B, as a single agent, inhibited growth of BxPC-3 cells in a dose dependent manner as well, with a relative IC50 value of 2.7 μM. BPI-2009H and BPI-403B were tested up to 50μM in Panc-1 cells with no apparent effect at the upper limit of the study for either of the compounds. In vivo, the mice treated with BPI-403B demonstrated a statistically significant tumor growth delay, 14.3 days. 20% of the mice experienced tumor regression. The compound was well tolerated with minimal body weight loss. At low doses, BPI-2009H did not show any statistically significant tumor growth delay, but upon increasing the dose to the MTD, significant signs of anticancer activity was demonstrated, with an increase in tumor growth delay. Conclusions: The in vitro and in vivo findings show that both BPI-2009H and BPI-403B have antiproliferative effects against BxPC-3 pancreatic cancer cells. These compounds are both well tolerated and may prove to be an alternative option of EGFR-TKI to erlotinib treatment in pancreatic cancer cases. Citation Format: Victoria Lynn Wilde, Don Zhang, Jirong Peng, Michael A. Green, Michael N. Greco, Michael Costanzo. Anti-tumor activity of icotinib (BPI-2009H) and BPI-403B in the BxPC-3 pancreatic cancer cell line. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2592. doi:10.1158/1538-7445.AM2015-2592

514. Targeting the Negative Immune Regulatory Molecule B7-H4 on Both Tumor and Normal Tissue With Anti-B7-H4 CAR T Cells

B7-H4 is a negative immune regulatory molecule frequently overexpressed on the surface of cancer cells and immunosuppressive tumor-associated macrophages (TAMs). Ligation of B7-H4 with an unknown receptor on activated T cells results in inhibited effector function via cell cycle arrest, decreased proliferation and reduced IL-2 production. B7-H4 expression levels in ovarian cancer inversely correlate with patient survival, making B7-H4 an attractive candidate for therapeutic intervention. However, trials of B7-H4 targeted therapy have not been conducted and the biodistribution of B7-H4 protein in mice or humans is not well understood.Here, we tested the hypothesis that safe and effective B7-H4 targeting can be achieved using T cells genetically redirected with chimeric antigen receptors (CARs) against B7-H4 in a preclinical model of human ovarian cancer. Four independent anti-B7-H4 CAR lentivirus constructs were generated using anti-B7H4 single chain variable fragments (scFv) with affinities ranging from low to high, which were transduced into primary human T cells. Transduced T cells efficiently expressed CARs on their cell surface, and each CAR was capable of binding both human and mouse recombinant B7-H4 protein with distinct binding patterns; two CARs (3#68 and 3#54) had high capacity for rhB7-H4 protein binding, another had low binding capacity (56), and the last had virtually none (26). In co-culture assays, high binding B7-H4 CAR T cells secreted Th1 cytokines and specifically lysed human B7-H4+ ovarian cancer cells. In an immunodeficient mouse model, transferred B7-H4 CAR T cells persisted after infusion and exerted efficient anti-tumor activity against subcutaneous B7-H4+ human ovarian tumor xenografts.Unexpectedly, B7-H4 CAR T cell treated mice reproducibly showed signs of delayed onset, lethal toxicity emerging 6-8 weeks after therapy. Postmortem analysis revealed widespread immunopathology in nearly all tissue analyzed, with marked infiltration and destruction of peripheral nerve bundles and perivasculature regions that was inconsistent with non-specific graft versus host disease (GVHD). Immunopathology was evident in both tumor-bearing and healthy mice administered B7-H-4 CAR T cells, and mice administered control CAR T cells experienced tumor regression but without concomitant toxicity, ruling out a generalizable GVHD effect.Our results indicate that CAR T cell-based targeting of B7-H4 can mediate control of B7-H4+ cancer outgrowth in vivo, however, long-term engraftment of B7-H4 CAR T cells mediates lethal on-target, off-tumor toxicity that is likely due to wide expression of B7-H4 in healthy mouse organs. Accordingly, B7-H4 CAR T cells represent an important preclinical model system for the evaluation of safety approaches that limit CAR-mediated toxicity whilst maintaining potent anti-tumor activity in vivo.

Abstract 4658: Use of a defined oleander extract by advanced cancer patients: Case reports on toxicity and tumor-related outcomes

Abstract The present study reports cases of advanced cancer patient taking an extract of Nerium oleander now in Phase 1 clinical trials in cancer patients. A phytochemical constituent of the extract, oleandrin, has multiple anticancer activities including inhibition of NF-kappaB and induction of apoptosis. We present case reports of 9 metastatic cancer patients who received the extract on personal use exemptions. Five of the patients also received full integrative programs at an integrative medicine center. Cases included 4 colon cancer patients, 3 pancreatic cancer patients (1 neuroendocrine and 2 adenocarcinoma), 1 renal cell carcinoma and 1 lung cancer patient. For the patients at the integrative center, all of whom took the extract during periods when they were receiving chemotherapy, toxicity grading of chemotherapy side effects was performed. We analyzed the case records for potential effects of the extract on tumor regression/stability in the absence of chemotherapy, survival time, use concurrent with chemotherapy and toxicity. The renal cell patient experienced tumor regression for 12 months with the extract alone; the 3 pancreatic cancer patients and a colon cancer patient experienced disease stabilization. Survival times were extended for all patients with survival times ranging from 32 months to 11 years for these patients with metastatic disease. Chemotherapy was well tolerated by colon cancer patients with only grade 1-2 toxicity during as many as 70 cycles of chemotherapy. Mild toxicities thought to be related to the extract included lightheadedness and mild tingling and burning of the mouth with use of the sublingual preparation. Severe toxicities including one myocardial infarction and one deep-vein thrombosis were observed but not suspected to be related to the extract. Good clinical outcomes and low toxicity were thus observed for the extract in these patients. Citation Format: Keith I. Block, Charlotte Gyllenhaal, Robert A. Newman. Use of a defined oleander extract by advanced cancer patients: Case reports on toxicity and tumor-related outcomes. [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 4658. doi:10.1158/1538-7445.AM2014-4658

Primary and acquired resistance to EGFR-targeted therapies in colorectal cancer: impact on future treatment strategies.

Only approximately 10 % of genetically unselected patients with chemorefractory metastatic colorectal cancer experience tumor regression when treated with the anti-epidermal growth factor receptor (EGFR) antibodies cetuximab or panitumumab (“primary” or “de novo” resistance). Moreover, nearly all patients whose tumors initially respond inevitably become refractory (“secondary” or “acquired” resistance). An ever-increasing number of predictors of both primary and acquired resistance to anti-EGFR antibodies have been described, and it is now evident that most of the underlying mechanisms significantly overlap. By trying to extrapolate a unifying perspective out of many idiosyncratic details, here, we discuss the molecular underpinnings of therapeutic resistance, summarize research efforts aimed to improve patient selection, and present alternative therapeutic strategies that are now under development to increase response and combat relapse.

Cancer immunotherapy based on mutation-specific CD4+ T cells in a patient with epithelial cancer.

Limited evidence exists that humans mount a mutation-specific T cell response to epithelial cancers. We used a whole-exomic-sequencing-based approach to demonstrate that tumor-infiltrating lymphocytes (TIL) from a patient with metastatic cholangiocarcinoma contained CD4+ T helper 1 (T(H)1) cells recognizing a mutation in erbb2 interacting protein (ERBB2IP) expressed by the cancer. After adoptive transfer of TIL containing about 25% mutation-specific polyfunctional T(H)1 cells, the patient achieved a decrease in target lesions with prolonged stabilization of disease. Upon disease progression, the patient was retreated with a >95% pure population of mutation-reactive T(H)1 cells and again experienced tumor regression. These results provide evidence that a CD4+ T cell response against a mutated antigen can be harnessed to mediate regression of a metastatic epithelial cancer.

Pilot study of intense neoadjuvant chemoradiotherapy for locally advanced rectal cancer: retrospective review of a phase II study.

Locally advanced rectal adenocarcinoma is typically treated with neoadjuvant chemoradiotherapy and surgery. We assessed the effect of an additional cycle of capecitabine/oxaliplatin chemotherapy before surgery in 57 patients with T3/4, N+/- or T1/2, N+ rectal cancer. MATERIALS AND STUDY DESIGN: Radiotherapy (total dose, 50.4 Gy) was combined with three cycles of chemotherapy (two cycles concomitant with radiotherapy), and each cycle consisted of oxaliplatin (130 mg/m2 on day 1) and capecitabine (825 mg/m2, twice per day from day 1 to day 14) for 21 days. In addition to assessing the safety of this treatment, the primary endpoint was pathological complete response (pCR). The secondary endpoint was the change in primary tumor and node stage from pre-treatment to post-surgery. Eleven patients (19%) experienced complete tumor regression and 23 patients (40%) experienced tumor regression grade 3. Tumor down-staging occurred in 31 patients (54.4%) and down-staging of nodes occurred in 25 patients (43.9%). There was a significant difference in tumor stage between pre-treatment and post-surgery (P <0.001). Patients with less advanced N stages had significantly better recurrence-free survival but similar metastasis-free survival and overall survival. Tumor regression grade was not associated with overall survival, recurrence-free survival or metastasis-free survival. The most common adverse events were pulmonary infection (n = 6, 10.5%) and intestinal obstruction (n = 6, 10.5%): CONCLUSIONS. An additional cycle of chemotherapy given after chemoradiotherapy and before surgery provided good efficacy and had a satisfactory safety profile in patients with locally advanced rectal cancer.

Gamma Knife in the Treatment of Pituitary Adenomas: Results of a Single Center

Gamma Knife (GK) radiosurgery for pituitary adenomas can offer a means of tumor and biologic control with acceptable risk and low complication rates. Retrospective review of all the patients treated at our center with GK for pituitary adenomas from Nov 2003 to June 2011. We treated a total of 86 patients. Ten were lost to follow-up. Mean follow was 32.8 months. There were 21 (24.4%) growth hormone secreting adenomas (GH), 8 (9.3%) prolactinomas (PRL), 8 (9.3%) adrenocorticotropic hormone secreting (ACTH) adenomas, 2 (2.3%) follicle stimulating hormone/luteinizing hormone secreting (FSH/LH) adenomas, and 47 (54.7%) null cell pituitary adenomas that were treated. Average maximum tumor diameter and volume was 2.21cm and 5.41cm³, respectively. The average dose to the 50% isodose line was 14.2 Gy and 23.6 Gy for secreting and non-secreting adenomas respectively. Mean maximal optic nerve dose was 8.87 Gy. Local control rate was 75 of 76 (98.7%), for those with followup. Thirty-three (43.4%) patients experienced arrest of tumor growth, while 42 (55.2%) patients experienced tumor regression. Of the 39 patients with secreting pituitary tumors, 6 were lost to follow-up. Improved endocrine status occurred in 16 (50.0%), while 14 (43.8%) demonstrated stability of hormone status on continued pre-operative medical management. Permanent complications included: panhypopituitarism (4), hypothyroidism (4), hypocortisolemia (1), diabetes insipidus (1), apoplexy (1), visual field defect (2), and diplopia (1). Gamma Knife radiosurgery is a safe and effective means of achieving tumor growth control and endocrine remission/stability in pituitary adenomas.

Antitumor activity of cabozantinib (XL184) in a cohort of patients (pts) with differentiated thyroid cancer (DTC).

5547 Background: Cabozantinib (cabo) is an oral, potent inhibitor of MET, VEGFR2, and RET that is currently undergoing evaluation in several oncology indications. Differentiated thyroid cancer (DTC) pts were included in this study based on involvement of the MET, VEGFR, and RET signaling pathways in this disease. The primary objective of this study is to determine the effect of cabo on single dose PK of the CYP2C8 substrate rosiglitazone (rosi). Anti-tumor activity and safety were also evaluated. Methods: Metastatic DTC pts who were enrolled to this study were required to be RAI-refractory, have progressed on standard therapies and have measurable disease. Cabo was given daily at a dose of 140 mg free base (equivalent to 175mg salt form) starting at Day 2. Rosi (4mg) was given Day 1 and Day 22 to complete PK assessment for drug-drug interaction (DDI). Cabo was continued until PD. On Day 57 and every 8 weeks thereafter subjects underwent tumor assessments by mRECIST. Results: 15 DTC pts were enrolled. Median number of prior regimens was 2 (11/15 pts had at least 1 prior VEGFR inhibitor). 8/15 pts (53%) had confirmed PRs including 1 pt with marked improvement of a bone infiltrating lesion; 6 (40%) had best response of SD; all 14 pts with ≥1 post-baseline scan experienced tumor regression (range: -9 to -55%). Disease control rate (PR + SD): 80% at 16 weeks; 10/15 (67%) remain on cabo with a median follow-up of 7.3 months. Median PFS and OS have not been reached. Most common Gr 3/4 AEs were: diarrhea (20%), lipase increased (20%), hypertension (13%) and palmar-plantar erythrodyesthesia (13%); one related Gr 5 event reported: hemoptysis due to aorto-trachael fistula in a pt with history of prior mediastinal XRT and extensive neck surgeries. PK data suggest that clinically relevant doses of cabo do not alter the Cmax or AUC0-24h of rosi, consistent with no inhibition of CYP2C8. Conclusions: In pts with DTC, cabo treatment resulted in substantial anti-tumor activity. The safety profile of cabo was comparable to that seen with other VEGFR TKIs. PK data suggest no DDI between cabo and rosi (CYP2C8 substrate).

Efficacy of cabozantinib (XL184) in patients (pts) with metastatic, refractory renal cell carcinoma (RCC).

4504 Background: Cabozantinib (cabo) is an oral, potent inhibitor of MET and VEGFR2 that is currently undergoing evaluation in several oncology indications. Renal cell carcinoma (RCC) was chosen as an indication in this drug-drug interaction (DDI) study based on involvement of the MET and VEGFR signaling pathways in this disease. The primary objective of this study is to determine the effect of cabo on single dose PK of the CYP2C8 substrate rosiglitazone (rosi). Anti-tumor activity was also evaluated. Methods: Eligible pts were required to have RCC with clear cell components with metastases, Karnofsky performance status of ≥70 and measurable disease by RECIST. Pts needed to have experienced PD following standard therapies. Cabo was given daily at a dose of 140 mg free base (equivalent to 175 mg salt form) starting at Day 2. Rosi (4 mg) was given Day 1 and Day 22 to complete PK assessment for DDI. Cabo was continued until PD. On Day 57 and every 8 weeks thereafter subjects underwent tumor assessments by mRECIST. Results: Enrollment is complete at 25 RCC pts; 17/25 (64%) RCC pts had received ≥ 2 prior agents; 13/25 (52%) with at least 1 VEGF pathway inhibitor and 1 mTOR inhibitor. The majority of pts were in an intermediate (21/25) or poor (3/25) prognostic category (1/25 in favorable category) per Heng et al (JCO, 2009, v27, p5794). ORR by mRECIST: 7/25 (28%). Disease control rate (PR + SD): 72% at 16 weeks; 19/21 (90%) pts with ≥1 post-baseline scan experienced tumor regression (range: 4 - 63% reduction in measurements). 10/25 (36%) pts remain on cabo. Median PFS is 14.7 months (95% CI: 7.3, upper limit not reached) with a median follow-up of 7.7 months. AEs ≥ Grade 3 severity: hypophosphatemia (36%), hyponatremia (20%), and fatigue (16%). PK data suggest that clinically relevant doses of cabo do not alter the Cmax or AUC0-24h of rosi, consistent with no inhibition of CYP2C8. Conclusions: Cabo demonstrates encouraging anti-tumor activity in heavily pretreated RCC pts with a toxicity profile similar to that of other VEGFR TKIs. PK data suggest no DDI between cabo and rosi (CYP2C8 substrate).

Detection and Characterization of a Novel Subset of CD8+CD57+ T Cells in Metastatic Melanoma with an Incompletely Differentiated Phenotype

Tumor-specific T cells are frequently induced naturally in melanoma patients and infiltrate tumors. It is enigmatic why these patients fail to experience tumor regression. Given that CD8(+) T cells mediate antigen-specific killing of tumor cells, the focus of this study was to identify alterations in the differentiation of CD8(+) residing at the tumor site, with emphasis on a population expressing CD57, a marker for terminal differentiation. We conducted flow cytometric analysis of CD8(+) tumor-infiltrating lymphocytes (TIL) isolated from 44 resected melanoma metastases with known T-cell differentiation markers. For comparison, peripheral blood mononuclear cells were isolated from matched melanoma patients. We sorted different CD8(+) subsets found in TIL and determined their effector functions. In addition, we carried out Vβ clonotype expression analysis of T-cell receptors to determine lineage relationship between the CD8(+) TIL subsets. The majority of CD8(+) TIL was in the early-effector memory stage of differentiation. A significant population consisted of an oligoclonal subset of cells coexpressing CD27, CD28, CD57, and Granzyme B, with little or no perforin. These cells could be induced to proliferate, produce a high level of IFN-γ, and differentiate into CD27(-)CD57(+), perforin(high) mature CTL in vitro. Addition of TGF-β1 prevented further differentiation. Our studies identified a novel subset of incompletely differentiated CD8(+) CTL coexpressing early effector memory and late CTL markers. This population resembles that found in patients with uncontrolled chronic viral infections. TGF-β1, frequently produced by melanoma tumors, may be a key cytokine inhibiting further maturation of this subset.

Activity of cabozantinib (XL184) in patients (pts) with metastatic, refractory renal cell carcinoma (RCC).

364 Background: Cabozantinib (cabo) is an oral, potent inhibitor of MET and VEGFR2 that is currently undergoing clinical efficacy evaluation in several oncology indications. Renal cell carcinoma (RCC) was chosen as an indication in this drug-drug interaction (DDI) study based on involvement of the MET and VEGFR signaling pathways in this disease. The primary objective of this study is to determine the effect of cabo on single dose PK of the CYP2C8 substrate rosiglitazone (rosi). The exploratory objective of this study is to evaluate the preliminary antitumor activity of cabo in pts with RCC. Methods: Eligible pts were required to have RCC with clear cell components with metastases, Karnofsky performance status of ≥70 and measurable disease by RECIST. Pts needed to have experienced PD following standard therapies. Method for DDI study: Day 1, 4 mg rosi; Days 2 - 22, cabo given daily at a dose of 175 mg; Day 22, 4 mg rosi to complete PK assessment for DDI. Cabo continued until PD. On Day 57 and every 8 weeks thereafter subjects underwent tumor assessments by mRECIST. Results: Enrollment is complete at 25 RCC pts with a median of 2 prior regimens; 17/25 (68%) RCC pts had received ≥ 2 lines of prior therapy and 13/25 (52%) with at least 1 VEGF pathway inhibitor and 1 mTOR inhibitor. All pts were intermediate (24/25) or poor (1/25) risk category per Heng et al prognostic strata (JCO 2009). Related AEs ≥ Grade 3 severity: hypophosphatemia 8 (32%), PE 3 (12%; all were incidental / resolved) and diarrhea 3 (12%). Preliminary PK data suggest that clinically relevant doses of cabo do not markedly alter the Cmax or AUC0-24h of rosi consistent with lack of inhibition of CYP2C8. RCC pts with confirmed PR by mRECIST: 6/25 (24%). Additionally, 1 pt had an unconfirmed PR. Disease control rate (PR + SD): 68% at 16 weeks; 18/21 (86%) pts with ≥1 post-baseline scan experienced tumor regression (range: 4 – 63% reduction in measurements). 14/25 (56%) remain on cabo with a median follow-up of 4 months. Median PFS and OS have not been reached. Conclusions: Cabo demonstrates encouraging anti-tumor activity in heavily pretreated pts with RCC with a toxicity profile similar to that of other TKIs. Preliminary data suggest no DDI between cabo and rosi (CYP2C8 substrate).

A phase II trial of chemotherapy plus hormone therapy as initial treatment of unresectable/metastatic adenocarcinoma of the prostate.

247 Background: Chemotherapy for hormone-refractory prostate cancer reduces PSA levels and enhances overall survival (OS), suggesting that administration in earlier disease stages may be beneficial. If expansion of an androgen-independent clone is present during androgen deprivation mediates the transformation from an androgen-dependent to an androgen-independent phenotype, combination chemohormonal therapy could be effective initial treatment for locally advanced or metastatic prostate cancer. This study examined the efficacy and safety of chemohormal therapy approach. Methods: Patients received medical castration plus an anti-androgen and chemotherapy (nab-paclitaxel, leuprolide, bicalutamide). Patients were followed with PSA levels and radiographic assessments. Results: Forty-six men (median age) 64.7 years were treated. Fifty-eight percent underwent prior local therapy including prostatectomy (30%), prior radiation (15%), or both (13%). Median baseline PSA was 8.9 ng/ml, and 96% of patients had a Gleason score of ≥7%. At 2 years, 78% of patients experienced tumor regression with a median reduction in PSA level of &gt;90%. Median time to progression was 28.43 months measured by PSA and 34.52 months measured radiographically. Median OS was 62.4 months. The most frequent significant adverse events included grade 3 hypokalemia (17%) and lymphopenia (59%). Conclusions: Combination chemohormonal therapy for locally advanced and metastatic prostate cancer delayed disease progression and enhanced OS. Information presented will include curves and correlation detailing efficacy and adverse events of various sub-populations.

Antitumor activity observed in a phase I drug–drug interaction study of cabozantinib (XL184) and rosiglitazone in patients (pts) with renal cell carcinoma (RCC) and differentiated thyroid cancer (DTC).

e13042 Background: Cabozantinib is an oral, potent inhibitor of MET and VEGFR2 that is currently undergoing clinical efficacy evaluation in several oncology indications. In parallel, clinical pharmacology studies are being performed, including assessment of potential drug-drug interactions (DDIs). Renal cell carcinoma (RCC) and differentiated thyroid cancer (DTC) were chosen as indications in this study based on involvement of the MET and VEGFR signaling pathways in these indications. The primary objective of this study is to determine the effect of cabozantinib on single dose PK of the CYP2C8 substrate rosiglitazone. The exploratory objective of this study is to evaluate the preliminary antitumor activity of cabozantinib in pts with RCC and DTC. Methods: Approximately 35 cancer pts initially limited to DTC or RCC may be enrolled to this study. On study Day 1, pts receive a 4 mg tablet of rosiglitazone; PK sampling is completed on Day 2. On Days 2 (post PK sampling) through 21, cabozantinib is administered daily at a starting dose of 175 mg. On study Day 22 pts receive rosiglitazone 4 mg tablet and complete PK assessments. On study Day 57 and every 8 weeks thereafter subjects undergo tumor assessments by mRECIST. Results: To date, 10 pts (9 RCC; 1 DTC) have been enrolled (20 pts anticipated by May 2011). All pts had measurable disease. Median number of prior regimens was 3 (7/9 RCC pts with ≥ 2 lines of prior therapy and 6/9 with at least 1 VEGF pathway inhibitor and 1 mTOR inhibitor). No marked differences in concentration profiles, Tmax, Cmax, or AUC0-24h values were observed in 4 pts who completed the PK portion. Overall, 4/9 RCC pts had a confirmed partial response; 7/10 pts experienced tumor regression (16-49%). Related AEs ≥Grade 3 severity: fatigue (1 pt), amylase and lipase increased and hypophosphatemia (1 pt), and hyponatremia and hypophosphatemia (1 pt). Conclusions: Preliminary data suggests no drug-drug interactions between cabozantinib and rosiglitazone (CYP2C8 substrate). Cabozantinib demonstrates anti-tumor activity in heavily pretreated pts with RCC.

C19orf48Encodes a Minor Histocompatibility Antigen Recognized by CD8+ Cytotoxic T Cells from Renal Cell Carcinoma Patients

Tumor regression has been observed in some patients with metastatic renal cell carcinoma (RCC) after nonmyeloablative allogeneic hematopoietic cell transplantation (HCT). Cellular and molecular characterization of antigens recognized by tumor-reactive T cells isolated from responding patients could potentially provide insight into the mechanisms of tumor regression. CD8+ CTL clones that recognized a novel RCC-associated minor histocompatibility (H) antigen presented by HLA-A*0201 were isolated from two patients with metastatic RCC who experienced tumor regression or stable disease following nonmyeloablative allogeneic HCT. These clones were used to screen a cDNA library and isolate the unique cDNA encoding the antigen. An alternative open reading frame in the C19orf48 gene located on chromosome 19q13 encodes the HLA-A*0201-restricted minor H antigen recognized by the RCC-reactive T cells. The differential T-cell recognition of donor- and recipient-derived target cells is attributable to a nonsynonymous single-nucleotide polymorphism within the nucleotide interval that encodes the antigenic peptide. Assays for gene expression and CTL recognition showed that the C19orf48-encoded peptide is widely expressed in renal tumors and solid tumors of other histologies. The antigenic peptide can be processed for CTL recognition via both TAP-dependent and TAP-independent pathways. Donor T-cell responses against the HLA-A*0201-restricted minor H antigen encoded by C19orf48 may contribute to RCC regression after MHC-matched allogeneic HCT.

Vaccination of a Melanoma Patient with Mature Dendritic Cells Pulsed with MAGE-3 Peptides Triggers the Activity of Nonvaccine Anti-Tumor Cells

We previously characterized the CTL response of a melanoma patient who experienced tumor regression following vaccination with an ALVAC virus coding for a MAGE-A3 Ag. Whereas anti-vaccine CTL were rare in the blood and inside metastases of this patient, anti-tumor CTL recognizing other tumor Ags, mainly MAGE-C2, were 100 times more frequent in the blood and considerably enriched in metastases following vaccination. In this study we report the analysis of the CTL response of a second melanoma patient who showed a mixed tumor response after vaccination with dendritic cells pulsed with two MAGE-A3 antigenic peptides presented, respectively, by HLA-A1 and HLA-DP4. Anti-MAGE-3.A1 CD8 and anti-MAGE-3.DP4 CD4 T cells became detectable in the blood after vaccination at a frequency of approximately 10(-5) among the CD8 or CD4 T cells, respectively, and they were slightly enriched in slowly progressing metastases. Additional anti-tumor CTL were present in the blood at a frequency of 2x10(-4) among the CD8 T cells and, among these, an anti-MAGE-C2 CTL clone was detected only following vaccination and was enriched by >1,000-fold in metastases relative to the blood. The striking similarity of these results with our previous observations further supports the hypothesis that the induction of a few anti-vaccine T cells may prime or restimulate additional anti-tumor T cell clones that are mainly responsible for the tumor regression.

Evaluation of AZD2171, an oral, highly potent and selective VEGFR signaling inhibitor, in renal cell carcinoma (RCC): Combined results from two phase I studies

3560 Background: Antiangiogenic agents have recently demonstrated promising activity in patients with advanced RCC. AZD2171 is an oral, highly potent and selective inhibitor of VEGFR-1, -2 and -3 tyrosine kinases, and is currently in Phase II/III development in NSCLC and CRC. Safety and efficacy results are presented for patients with RCC who participated in two Phase I dose-escalation studies of AZD2171 in advanced solid tumors. Methods: Patients with advanced recurrent metastatic RCC received once-daily oral AZD2171, either as monotherapy (Drevs et al. Proc Am Soc Clin Oncol 2005: abst 3002; completed) or in combination with gefitinib (van Cruijsen et al. Proc Am Soc Clin Oncol 2006: abst 3017; ongoing). All patients had received prior interferon-a ± interleukin-2/ 5-FU or radiotherapy. Results: Twenty-one patients received AZD2171, 4 as monotherapy (20 mg, n=1; 60 mg, n=3) and 17 as combination therapy (AZD2171 20–45 mg with gefitinib 250 or 500 mg). The adverse event (AE) profile in RCC patients was similar to that reported previously for all patients in these studies; hypertension, dysphonia, nausea, vomiting, diarrhea and fatigue were the most common AEs. The most common CTC grade 3 AEs were hypertension (n=5) and diarrhea (n=4). Reductions in plasma levels of sVEGFR-2 were observed in RCC patients when AZD2171 was administered as a monotherapy or in combination with gefitinib; the reductions in the combination study were dose- and time-dependent (sustained). Nineteen patients were evaluable for efficacy (RECIST): 2/3 monotherapy patients experienced tumor regression, one of which was confirmed as a partial response (duration of response [DR] 87 days); in the combination study, 6/16 (38%) patients achieved a partial response (median DR 6 months; 3/6 ongoing at data cut off) and 7/16 (44%) patients had stable disease (4/7 had a confirmed 10–30% reduction in maximum tumor diameter). Conclusion: AZD2171, both as monotherapy and in combination with gefitinib, showed encouraging antitumor activity and a manageable toxicity profile in patients with advanced RCC who had failed prior therapy. A randomized Phase II investigation of AZD2171 monotherapy (45 mg/day) vs placebo in patients with advanced RCC is ongoing. [Table: see text]

Reduced-Intensity Cord Blood Transplantation (RICBT) Is a Feasible Approach for Advanced Adult T-Cell Leukemia (ATL).

Introduction:ATL in advanced stage is a lymphoid malignancy with poor prognosis, its mean survival time being a few months. Allogeneic hematopoietic stem cell transplantation has been shown to be potentially curative approach, but the availability of HLA-matched donor, either of related or unrelated, limits its application to many of the patients. Cord blood has been widely used as an alternative donor cells. We report here the feasibility of RICBT for patients with advanced ATL.Patients and Methods:Eighteen patients with advanced ATL, including 11 acute type and 7 lymphoma type, who underwent RICBT between March 2002 and June 2005 at our institution, were retrospectively analyzed. Eighty percent of them were chemo-refractory at the time of transplant. Median age of the patients was 59 years (27–79). Pretransplant conditioning regimen consisted of fludarabine 125 mg/m2, melphalan 80 mg/m2 and TBI 4 Gy. GVHD prophylaxis was either cyclosporine (CSP, n=11) or tacrolimus (TAC, n=7) alone. The median number of infused nucleated cells and CD34 positive cells were 2.83 (1.95–4.83) x 107 and 1.00 (0.40–2.91) x 105, respectively. All the patients received CB units with HLA mismatches at 1 (n=8) or 2 (n=10) loci.Results:Neutrophil and platelet engraftment were observed in 15 (83.3%, median 16 days) and 14 patients (77.8 %, median 42 days). Two died before engraftment. Five of the engrafted patients (30%) developed acute GVHD (grade II–IV). Although 14 out of 15 patients who survived over 30 days achieved complete remission, 6 died of non-relapse mortality (NRM) within 100 days post-transplant (5 sepsis, 1 encephalitis), and another 6 died of relapse (median 225 days post-transplant). Five of the 7 patients who were alive beyond 100 days developed chronic GVHD (4 limited, 1 extensive). One patient experienced rapid tumor regression along with the chronic GVHD after cessation of TAC at day 146 post-transplant, indicating possible GvATL effect. Estimated 1-year overall and progression-free survival rates were 27.9 +/− 9.0 % and 17.2 +/− 12.8 %, respectively. Among 9 survivors beyond 100 days post-transplant, 5 remain alive at median follow-up of 17 months but only 2 of them remain progression free. Univariate analyses revealed high age (over 60), poor ECOG performance status (over 2) and high sIL-2R level (over 10000IU/L) as poor factors for survival. TAC dramatically decreased the day 100 mortality (14.3%) compared with CSP (45.5%).Conclusion:This pilot study indicates that our RICBT is feasible even for the ATL patients in advanced stage. Day 100 mortality was improved by using TAC but eventually the overall survival decreased to comparable level with CSP. To further improve the outcome, RICBT should be investigated for patients in early stage of the disease, or new approach to prevent late relapse should be explored.

Chemosensitization of Pancreatic Carcinoma Cells to Enhance T Cell-Mediated Cytotoxicity Induced by Tumor Lysate-Pulsed Dendritic Cells

Dendritic cells (DCs) can induce cytotoxic T-cell (CTL) responses against tumor antigens in vitro and in vivo, yet few cancer patients experience tumor regression after DC-based vaccination. Combination with other treatment modalities, such as radiation or pharmacologic anticancer agents, may reduce tumor cell resistance against immune responses. The authors tested whether treatment with gemcitabine or cyclooxygenase-2 (COX-2) inhibitors increases the sensitivity of pancreatic carcinoma cells to CTL-mediated killing. Monocyte-derived DCs of HLA-A2+ donors were loaded with lysate from the HLA-A2+ pancreatic carcinoma cell line Panc-1 and co-cultured with autologous CD3+ T cells. ELISPOT and cytotoxicity assays performed after two rounds of in vitro stimulation confirmed induction of a tumor-specific CTL response. Changes in the magnitude and the effector mechanism of the CTL response were analyzed after treatment of Panc-1 cells with gemcitabine and COX-2 inhibitors. Compared with gemcitabine, COX-2 inhibitors more effectively sensitized Panc-1 cells to CTL-mediated killing and showed less inhibition of T-cell activation by DCs in vitro. Using anti-CD95 blocking antibody, the authors showed that the increase in CTL-mediated tumor cell killing observed after treatment with COX-2 inhibitors is dependent on CD95/CD95 ligand interaction. Increased apoptosis of Panc-1 cells treated with COX-2 inhibitor was also observed after incubation with agonistic anti-CD95 antibody. Sensitization of cancer cells to CD95-dependent killing by CTLs represents a novel mechanism of action for COX-2 inhibitors and provides a rationale for their concomitant use with immunotherapeutic strategies such as DC-based vaccination.