Induction of double-strand breaks with the non-steroidal androgen receptor ligand flutamide in patients on androgen suppression: a study protocol for a randomized, double-blind prospective trial

BACKGROUND

Prostate cancer remains the most prevalent malignancy and the second-leading cause of cancer-related death in men in the USA. Radiation therapy, typically with androgen suppression, remains a mainstay in the treatment of intermediate- and high-risk, potentially lethal prostate cancers. However, local recurrence and treatment failure remain common. Basic and translational research has determined the potential for using androgen receptor (AR) ligands (e.g., dihydrotestosterone and flutamide) in the context of androgen-deprived prostate cancer to induce AR- and TOP2B-mediated DNA double-strand breaks (DSBs) and thereby synergistically enhance the effect of radiation therapy (RT). The primary aim of this study is to carry out pharmacodynamic translation of these findings to humans.

METHODS

Patients with newly diagnosed, biopsy-confirmed localized prostatic adenocarcinoma will be recruited. Flutamide, an oral non-steroidal androgen receptor ligand, will be administered orally 6-12 h prior to prostate biopsy (performed under anesthesia prior to brachytherapy seed implantation). Key study parameters will include the assessment of DNA double-strand breaks by γH2A.x foci and AR localization to the nucleus. The initial 6 patients will be treated in a single-arm run-in phase to assess futility by establishing whether at least 2 subjects from this group develop γH2A.x foci in prostate cancer cells. If this criterion is met, the study will advance to a two-arm, randomized controlled phase in which 24 participants will be randomized 2:1 to either flutamide intervention or placebo standard-of-care (with all patients receiving definitive brachytherapy). The key pharmacodynamic endpoint will be to assess whether the extent of γH2A.x foci (proportion of cancer cells positive and number of foci per cancer cell) is greater in patients receiving flutamide versus placebo. Secondary outcomes of this study include an optional, exploratory analysis that will (a) describe cancer-specific methylation patterns of cell-free DNA in plasma and urine and (b) assess the utility of serum and urine samples as a DNA-based biomarker for tracking therapeutic response.

DISCUSSION

This study will confirm in humans the pharmacodynamic effect of AR ligands to induce transient double-strand breaks when administered in the context of androgen deprivation as a novel therapy for prostate cancer. The findings of this study will permit the development of a larger trial evaluating flutamide pulsed-dose sequencing in association with fractionated external beam RT (+/- brachytherapy). The study is ongoing, and preliminary data collection and recruitment are underway; analysis has yet to be performed.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03507608. Prospectively registered on 25 April 2018.

Nelfinavir Inhibition of Kaposi's sarcoma-associated herpesvirus protein expression and capsid assembly

Background

Antiviral therapies that target herpesviruses are clinically important. Nelfinavir is a protease inhibitor that targets the human immunodeficiency virus (HIV) infections aspartyl protease. Previous studies demonstrated that this drug could also inhibit Kaposi's sarcoma-associated herpesvirus (KSHV) production. Our laboratory demonstrated nelfinavir can effectively inhibit herpes simplex virus type 1 (HSV-1) replication. For HSV-1 we were able to determine that virus capsids were assembled and exited the nucleus but did not mature in the cytoplasm indicating the drug inhibited secondary envelopment of virions.

Methods

For KSHV, we recently derived a tractable cell culture system that allowed us to analyze the virus replication cycle in detail. We used this system to further define the stage at which nelfinavir inhibits KSHV replication.

Results

We discovered that nelfinavir inhibits KSHV extracellular virus production. This was seen when the drug was incubated with the cells for 3 days and when we pulsed the cells with the drug for 1-5 minutes. When KSHV infected cells exposed to the drug were examined using ultrastructural methods there was an absence of mature capsids in the nucleus indicating a defect in capsid assembly. Because nelfinavir influences the integrated stress response (ISR), we examined the expression of viral proteins in the presence of the drug. We observed that the expression of many were significantly changed in the presence of drug. The accumulation of the capsid triplex protein ORF26 was markedly reduced. This is an essential protein required for herpesvirus capsid assembly.

Conclusions

Our studies confirm that nelfinavir inhibits KSHV virion production by disrupting virus assembly and maturation. Of interest is that inhibition requires only a short exposure to drug. The source of infectious virus in saliva has not been defined in detail but may well be lymphocytes or other cells in the oral mucosa. Thus, it might be that a "swish and spit" exposure rather than systemic administration would prevent virion production.

CTNI-60. PRELIMINARY RESULTS OF BINIMETINIB AND ENCORAFENIB IN ADULTS WITH RECURRENT BRAF V600E-MUTATED HIGH-GRADE GLIOMA

BACKGROUND

Although < 5% of high-grade gliomas (HGG) are BRAF-V600E mutated, these tumors are being identified more frequently as genetic testing increases in gliomas. Given the treatment-refractory nature HGG, RAF-targeted therapy is of special interest. The combination of encorafenib (BRAF inhibitor) with binimetinib (MEK inhibitor) was evaluated in adults with recurrent BRAFV600-mutated HGG.

METHODS

In this phase 2, open-label, Adult Brain Tumor Consortium trial(NCT03973918) encorafenib (450mg daily) and binimetinib (45mg twice daily) were administered continuously until disease progression, unacceptable toxicity, or death. Eligible patients had a histologically-confirmed HGG with BRAF-V600E mutation identified by PCR or next generation sequencing, and had progressed after radiation and any number of prior medical therapies. The primary endpoint was radiographic response rate by RANO criteria. Plasma was collected at baseline, on-study, and at progression for correlatives.

RESULTS

Five patients enrolled between January 2020 and November 2021. All patients had at least one prior recurrence (range 1-4) and received radiation one or more times. Median age was 27 years(range 22-77). Histopathologic diagnosis was glioblastoma(n = 2), anaplastic PXA(aPXA; n = 2), and anaplastic ganglioglioma(aGG; n = 1). Patients received treatment for 2-28months; currently 2/5 patients remain on treatment (8 and 30 months). Radiographic response rate was 60%(3/5): CR in two (glioblastoma, treated 10months; glioblastoma, 8months treatment ongoing), PR in one (aPXA, 28months treatment ongoing), SD in one (aGG, treated 3months), and PD in one (aPXA, treated 2months). Likely attributable adverse events (CTCAE grade ≥ 3) included cilioretinal artery occlusion (came off study) and asymptomatic elevated CPK. Analysis of paired plasma samples and correlation with response is ongoing.

CONCLUSIONS

Encorafenib and binimetinib demonstrate promising tumor responses in patients with recurrent BRAFV600E-mutated HGG with sustained responses in all GBM and 50% of aPXA in this small series, warranting careful consideration in this rare tumor subgroup. This Phase 2 study has closed due to enrollment issues

CTNI-26. SURGICAL WINDOW OF OPPORTUNITY TRIAL OF NAVTEMADLIN (KRT 232; AMG232) IN PATIENTS WITH RECURRENT GLIOBLASTOMA

BACKGROUND

KRT232 is an orally bioavailable, selective small molecule inhibitor of MDM2 that blocks the protein-protein interaction between MDM2 and p53. We performed a surgical window of opportunity trial of KRT232 in patients with recurrent GBM.

METHODS

The primary endpoint was to determine the tumor tissue concentration of KRT232. Prior to surgery, patients received KRT232 at either 120mg (n = 10, minimal dose that is consistently associated with alterations in serum MIC-1) or 240mg (n = 10; recommended phase 2 dose as monotherapy) for two days prior to surgical resection. Surgery was performed 3-6 hours following the last administration of KRT232. Tissue was analyzed for KRT232 concentration by LC/MS and for correlative studies. Participants with TP53 wild-type tumors were eligible to continue KRT232 following recovery from surgery at the RP2D of 240mg QD x 7 days q3weeks.

RESULTS

Twenty-one patients were enrolled from July 2018 to April 2020. One patient was deemed ineligible after surgery due to non-GBM tumor. Study met the prespecified criteria of target intra-tumor drug concentration of ≥ 25nM in contrast enhancing tissue in more than 50% of the patients in the 120mg cohort (67.1 ± 42.7nM in 8/10 patients) and 240mg (328.7 ± 468.1nM in 10/10 patients) cohort. Serum MIC-1 fold-changes from baseline (FCB) approximately 24 hours after a single dose of KRT232 were higher in the 240mg cohort (9.1 ± 4.1-FCB) than the 120mg cohort (3.6 ± 2.0-FCB). CDKN1A (p21), a downstream marker of p53, was significantly upregulated in analyzed participants whose GBM was TP53 wildtype, but not in TP53 mutant GBM or control samples (GBM treated with standard of care).

CONCLUSION

KRT232 at both 120mg and 240mg achieves adequate tumor tissue penetration and affects downstream pathways in TP53 wildtype GBM. The study has moved to Alliance to complete a phase 1 study of radiation + KRT232 in patients with newly diagnosed MGMT unmethylated GBM.

OUP accepted manuscript

Background

Persons living with human immunodeficiency virus are an underserved population for evidence-based cancer treatment. Paclitaxel and carboplatin (PCb) is an active regimen against a variety of solid tumors, including several seen in excess in patients with HIV infection. We performed a pilot trial to evaluate the safety of full-dose PCb in people living with human immunodeficiency virus and cancer.

Methods

Eligible patients, stratified by concurrent antiretroviral therapy (ART) that included CYP3A4 inhibitors or not, received paclitaxel (175 mg/m²) in combination with carboplatin (target AUC 6) intravenously every 3 weeks for up to 6 cycles.

Results

Sixteen evaluable patients received 64 cycles of PCb, including 6 patients treated with CYP3A4 inhibiting ART (ritonavir). The adverse event profile was consistent with the known toxicity profile of PCb, with no differences between the 2 strata. There were 4 partial responses (25%, 95% CI: 7%-52%), and overall, CD4+ lymphocyte count was similar after completion of therapy (median: 310/μL) compared with baseline values (median: 389/μL). Pharmacokinetic studies in 6 patients revealed no significant differences in C_max or AUC_inf for paclitaxel between the 2 cohorts.

Conclusion

Full doses of PCb chemotherapy are tolerable when given concurrently with ART in people living with human immunodeficiency virus with cancer, including patients receiving CYP3A4 inhibitors.

ClinicalTrials.gov Identifier

NCT01249443.

Preclinical evaluation of a hypotonic docetaxel nanosuspension formulation for intravesical treatment of non-muscle-invasive bladder cancer

Intravesical chemotherapy is a key approach for treating refractory non-muscle-invasive bladder cancer (NMIBC). However, the effectiveness of intravesical chemotherapy is limited by bladder tissue penetration and retention. Here, we describe the development of a docetaxel nanosuspension that, when paired with a low osmolality (hypotonic) vehicle, demonstrates increased uptake by the bladder urothelium with minimal systemic exposure. We compare the bladder residence time and efficacy in an immune-competent rat model of NMIBC to the clinical comparator, solubilized docetaxel (generic Taxotere) diluted for intravesical administration. We found that only the intravesical docetaxel nanosuspension significantly decreased cell proliferation compared to untreated tumor tissues. The results presented here suggest that the combination of nanoparticle-based chemotherapy and a hypotonic vehicle can provide more efficacious local drug delivery to bladder tissue for improved treatment of refractory NMIBC.

High-dose administration of tyrosine kinase inhibitors to improve clinical benefit: A systematic review

BACKGROUND

Innovative strategies to fully exploit the antitumor activity of multitargeted tyrosine kinase inhibitors (TKIs) are urgently needed. Higher concentrations of TKIs at their target site, i.e. intratumorally, may lead to broader kinase inhibition, which might be essential for the optimal suppression of tumor growth and induction of apoptosis. To reach these higher intratumoral concentrations, without encountering dose limiting toxicity, alternative TKI dosing strategies employing higher daily and high intermittent doses have been studied. In this systematic review, we evaluated the current clinical evidence to support (intermittent) high TKI dosing regimens.

METHODS

A systematic review was conducted in the following databases: PubMed®, EMBASE® and Cochrane Library©, to evaluate efficacy of alternatively scheduled high-dosed regimen (a higher dose in a regular daily schedule than registered or a higher dose in an alternative intermittent schedule) of TKIs in (haemato-)oncology. Data were extracted independently by two authors according to predefined criteria. Extracted data were tabulated to summarize key findings.

RESULTS

Out of twenty studies that met the inclusion criteria, thirteen investigated higher daily dose schedules of either afatinib, axitinib, erlotinib, gefitinib, imatinib, sorafenib, and sunitinib. Five of these studies included pharmacokinetic analyses, reporting marginal higher maximum drug concentrations (C_max) in plasma (1.3-4-fold higher) compared to the standard dose schedules. Seven clinical trials investigated intermittent high-dose schedules requiring treatment breaks, with the following TKIs: afatinib, erlotinib, gefitinib, lapatinib, sorafenib, and sunitinib. Six of these included pharmacokinetic results, all reporting higher (2-21-fold) C_max in plasma compared to the standard daily dose schedule, with manageable toxicity. No data on tumor concentrations were presented. Data on the efficacy outcomes were limited due to small sample size, study designs, phase 1 population and heterogeneous tumor types.

CONCLUSIONS

Early phase clinical studies show that high-dose intermittent TKI-treatment schedules can lead to an increased C_max compared to standard (low-dose) daily administration with manageable toxicity. These higher concentrations are assumed to reflect higher intratumoral concentrations. Further investigation of the potential improvement in clinical benefit of a high-dose intermittent strategy with multitargeting TKIs is warranted.

Contact atomic force microscopy using piezoresistive cantilevers in load force modulation mode

Scanning probe microscopy (SPM) encompasses several techniques for imaging of the physical and chemical material properties at nanoscale. The scanning process is based on the detection of the deflection of the cantilever, which is caused by near field interactions, while the tip runs over the sample's surface. The variety of deflection detection methods including optical, piezoresistive, piezoelectric technologies has been developed and applied depending on the measurement mode and measurement environment. There are many advantages (compactness, vacuum compatibility, etc.) of the piezoresistive detection method, which makes it very attractive for almost all SPM experiments. Due to the technological limitations the stiffness of the piezoresistive beams is usually higher than the stiffness of the cantilever detected using optical methods. This is the basic constraint for the application of the piezoresistive beams in contact mode (CM) atomic force microscopy (AFM) investigations performed at low load forces (usually less than 20 nN). Drift of the deflection signal, which is related to thermal fluctuations of the measurement setup, causes that the microscope controller compensates the fluctuations instead of compensating the strength of tip-surface interactions. Therefore, it is quite difficult to keep near field interaction precisely at the setpoint level during the whole scanning process. This can lead to either damage of the cantilever's tip and material surface or loosing the contact with the investigated sample and making the measurement unreliable. For these reasons, load force modulation (LoFM) scanning mode, in which the interaction at the tip is precisely controlled at every point of the sample surface, is proposed to enable precise AFM surface investigations using the piezoresistive cantilevers. In this article we describe the developed measurement algorithm as well as proposed and introduced hardware and software solutions. The results of the experiments confirm strong reduction of the AFM entire setup drift. The results demonstrating contactless tip lateral movements are presented. It is common knowledge that such a scanning reduces tip wear.

Phase I trial of maintenance sorafenib after allogeneic hematopoietic stem cell transplantation for fms-like tyrosine kinase 3 internal tandem duplication acute myeloid leukemia

The fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) mutation is associated with a high relapse rate for patients with acute myeloid leukemia (AML) even after allogeneic hematopoietic stem cell transplantation (HSCT). Sorafenib is a tyrosine kinase inhibitor, which inhibits the FLT3 tyrosine kinase and has shown encouraging activity in FLT3-ITD AML. We conducted a phase I trial of maintenance sorafenib after HSCT in patients with FLT3-ITD AML (ClinicalTrials.govNCT01398501). Patients received a variety of conditioning regimens and graft sources. A dose escalation 3 + 3 cohort design was used to define the maximum tolerated dose (MTD), with an additional 10 patients treated at the MTD. Sorafenib was initiated between days 45 and 120 after HSCT and continued for 12 28-day cycles. Twenty-two patients were enrolled (status at HSCT: first complete remission [CR1], n = 16; second complete remission [CR2], n = 3; refractory, n = 3). The MTD was established at 400 mg twice daily with 1 dose-limiting toxicity (DLT) observed (pericardial effusion). Two patients died of transplantation-related causes, both unrelated to sorafenib. Two patients stopped sorafenib after relapse and 5 stopped because of attributable toxicities after the DLT period. Median follow-up for surviving patients is 16.7 months after HSCT (range, 8.1 to 35.0). There was 1 case of grade II acute graft-versus-host disease (GVHD) after starting sorafenib and the 12-month cumulative incidence of chronic GVHD was 38% (90% confidence interval [CI], 21% to 56%). For all patients, 1-year progression-free survival (PFS) was 85% (90% CI, 66% to 94%) and 1-year overall survival (OS) was 95% (90% CI, 79% to 99%) after HSCT. For patients in CR1/CR2 before HSCT (n = 19), 1-year PFS was 95% (90% CI, 76% to 99%) and 1-year OS was 100%, with only 1 patient who relapsed. Sorafenib is safe after HSCT for FLT3-ITD AML and merits further investigation for the prevention of relapse.

Abstract B279: A phase I study determining the safety and tolerability of combination therapy with Pazopanib (P), a VEGFR/PDGFR/Raf inhibitor, and GSK1120212 (Trametinib: T), a MEK inhibitor, in advanced solid tumors with expansion cohorts in advanced differentiated thyroid cancer (DTC), cholangiocarcinoma (ChCA), and soft tissue sarcoma (STS)

Background: P is a small molecule tyrosine kinase inhibitor that selectively inhibits VEGFR1-3, PDGFR-α, PDGFR-β, c-kit, and FGFR 1-3 and is approved for renal cancer and STS. T is a potent, highly selective, allosteric inhibitor of MEK1/2 approved for BRAF-mutated advanced melanoma. Increased signaling of growth factor receptor tyrosine kinases have been shown to be important to cell survival in multiple tumor types, and their inhibition has been effective therapeutically in STS, DTC, and ChCa. In addition, increased RAS/RAF/MEK/ERK signaling plays a critical role in the development of many different types of cancers, including ChCA and DTC. We hypothesized that combination therapy with P and T would be tolerable and effective for this range of tumor types.

Methods: We designed a phase I, open label, dose escalation trial with P+T open to patients with advanced solid tumors. The study was a standard 3+3 design with an expansion cohort of 25 pts each for advanced DTC, STS, and ChCA for correlative endpoints and PK studies. Pts were treated with T held constant at 1 mg QD and P at 400 mg QD (DL1), 600 mg QD (DL2)and 800 mg QD (DL3); T was then escalated to 1.5 mg QD (DL4) and 2 mg QD (DL5). Eligibility included adequate end organ function, PS 0-1, and PD within 6 months in the expansion cohort of DTC. The primary objective was to determine the safety and tolerability of P+T and to find the MTD. Secondary objectives include assessing preliminary efficacy and exploration of PK/PD endpoints with tumor biopsies.

Results: We report the results of the dose escalation component of the study. 26 pts were accrued to 5 dose levels and treated for a median of 3 cycles (range <1-9.5). MTD was defined as DL5. There was one DLT on DL1 with gr3 fatigue and muscle weakness. There were no gr4 AEs at least possibly attributable to study therapy. Grade 3 AES attributable to study therapy were diarrhea and elevated transaminases (15%), HTN (12%), fatigue (8%), and proteinuria, muscle weakness, rash, or abdominal cramping (4%). Common gr1-2 AES included diarrhea (73%), nausea and rash (54%), fatigue (46%), HTN (38%), anorexia or vomiting (27%). 7 pts discontinued study tx due to AEs. 9 pts had dose reductions at a median of cycle 2 (range 1-9) due to HTN (3), diarrhea (3), fatigue (2), elevated transaminases or glaucoma exacerbation (1). Out of 25 evaluable pts, 3 had a partial response (ChCA, ovarian, DTC) and were treated 4-9.5 cycles and 16 had stable disease at least through first reassessment.

Conclusions: P+T is a tolerable combination with some preliminary signs of efficacy. Accrual to expansion cohorts in DTC, STS, and ChCA for further exploration of efficacy and correlative endpoints is ongoing. This study was approved and funded by the National Comprehensive Cancer Network (NCCN) from general research support provided by GlaxoSmithKline.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B279.

Citation Format: Nilofer Azad, Douglas Ball, Steven Sherman, Michelle Rudek, Gerald Falchook, Barry Nelkin, Filip Janku, Nicholas Papadopoulos, Ashley O'Conner, Shabina Ahmed, Breelyn Wilky, Susan Markus, Jing Gong, David Cosgrove, Marianna Zahurak, Ralph Zinner, Razelle Kurzrock. A phase I study determining the safety and tolerability of combination therapy with Pazopanib (P), a VEGFR/PDGFR/Raf inhibitor, and GSK1120212 (Trametinib: T), a MEK inhibitor, in advanced solid tumors with expansion cohorts in advanced differentiated thyroid cancer (DTC), cholangiocarcinoma (ChCA), and soft tissue sarcoma (STS). [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B279.

Abstract B74: A Phase I trial of vertical inhibition of IGF signaling using IMC-A12, an IGF1-R inhibitor, and AZD6244, a MEK 1/2 inhibitor, in patients with advanced solid tumors

Background: The IGF1 receptor activates key pro-survival signaling pathways critical in cancer including the RAS/RAF/MEK/ERK and PI3K/mTOR/AKT pathways. Despite this, clinical trials of single-agent IGF1-R antibodies have shown modest clinical benefit. In vitro data suggests that dual inhibition of IGF1-R and MEK synergistically decreases downstream pathway activation and increases apoptosis. Therefore, we performed a phase I clinical trial to test the safety and toxicity of combined IMC-A12 (anti-IGF1-R antibody) and AZD6244 (MEK 1/2 inhibitor).

Methods: Patients were required to have advanced solid tumors refractory to standard therapy with adequate performance status and end-organ function. Treatment consisted of AZD6244 hydrogen sulfate capsules orally twice daily, and IMC-A12 intravenously on days 1 and 15 of each 28-day cycle. The study was a 3+3 design, with a dose-finding cohort and an expansion cohort treated at the maximally tolerated dose. Pharmacokinetic studies were performed on all patients, while pre- and post-treatment biopsies for pharmacodynamic assessment of pathway activity were obtained from patients on the expansion cohort.

Results: 30 patients were enrolled on the study, 16 in the dose-finding cohort and 14 patients in the expansion cohort. The regimen was well-tolerated in most patients, and the most common study-drug related adverse events included rash, nausea/vomiting, diarrhea, and poor appetite/weight loss. Grade 3 or greater toxicities included nausea and vomiting, anemia, CVA, hypertension, hyperglycemia, and ophthalmologic symptoms (blurry vision, floaters, flashing lights, black dots/lines in field of vision, retinopathy). Three patients treated at dose level 2 (AZD6244 75 mg / IMC-A12 12 mg) developed dose-limiting toxicity of ophthalmologic symptoms; therefore the maximally tolerated combination dose was AZD6244 50 mg / IMC-A12 12 mg. 19 patients remained on study for at least 8 weeks and were evaluable for radiographic response. Two patients achieved a partial response (one unconfirmed), and 6 patients achieved progression-free survival of greater than 6 months. Two of the three patients with BRAF mutations showed prolonged progression-free survival on therapy. Pharmacokinetic analysis is ongoing. Paired pre- and on-treatment biopsies obtained in 5 patients showed significant suppression of phospho-ERK activity with treatment.

Conclusions: Vertical inhibition of IGF1-R mediated signaling aims to avoid compensatory escape mechanisms by inhibiting additional downstream targets within the RAS/RAF/MEK/ERK and/or PI3K/mTOR/AKT pathways. Our study of IMC-A12 and AZD6244 showed that the drug combination is safe and well-tolerated, with decreased phosphorylation of ERK indicating effective target inhibition. Further study is necessary to identify biomarkers for patients likely to benefit from this treatment approach, particularly with regards to patients possessing BRAF mutations.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B74.

Citation Format: Breelyn A. Wilky, Michelle Rudek, Daniel Laheru, David Cosgrove, Ross Donehower, Barry Nelkin, Douglas Ball, L. Austin Doyle, Helen Chen, Xiaobu Ye, Nilofer Azad. A Phase I trial of vertical inhibition of IGF signaling using IMC-A12, an IGF1-R inhibitor, and AZD6244, a MEK 1/2 inhibitor, in patients with advanced solid tumors. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B74.

Abstract 3494: Liver X receptor activation represents a novel strategy to block Hedgehog signaling in pancreatic adenocarcinoma and enhance the antitumor effect of gemcitabine

Background: The Hedgehog (Hh) signaling pathway plays a pathogenic role in many human cancers, including pancreatic adenocarcinoma, and several pathway antagonists have begun clinical testing. All of these novel agents target Smoothened (Smo), a key regulator of Hh signaling, but reported emergence of resistance mutations questions the durability of this approach. Oxysterols, oxidized derivatives of cholesterol, can modulate Hh signaling either through direct interaction with Smo or via cross-talk with liver X receptors (LXR) that serve as their natural receptors. Thus, oxysterols may represent mechanistically novel Hh inhibitors, especially if they involve LXRs. Methods: We examined the effects of LXR activation on the in vivo growth of pancreatic cancer. Nude mice bearing pancreatic cancer xenografts derived from primary clinical specimens were treated with a vehicle control, gemcitabine, the non-steroidal LXR agonist TO901317, or the combination of gemcitabine and TO901317 for 4-6 weeks. The LXR agonist TO901317 was used since it lacks the ability to directly bind to Smo. Tumor volumes were measured to assess response, and LXR and Hh pathway activities were quantified by real-time RT-PCR for Hh (GLI1, PTCH1) and LXR (ABCA1) target gene expression. Human specific primers were used to detect changes in tumor cells, whereas mouse-specific primers were used to study stroma. Intratumoral levels of gemcitabine triphosphate were quantified by LC-MS-MS. Results: Administration of TO901317 alone did not impact tumor growth compared to control treated animals similar to previous findings with Smo antagonists. Treatment with gemcitabine alone decreased tumor growth, However the addition of TO901317 to gemcitabine significantly enhanced this effect to promote tumor regression. In vivo treatment with TO901317 successfully activated LXR in both human tumor cells and murine stromal cells as evidenced by increased expression of ABCA1. Moreover, TO901317 inhibited expression of the Hh targets GLI1 and PTCH1 5- and 2-fold, respectively, in stromal cells and 5-fold in tumor cells. Previous studies (Olive et al, Science, 2009) demonstrated that Hh pathway inhibition improves drug delivery in vivo. Therefore, we quantified intratumoral levels of gemcitabine triphosphate, the active metabolite of gemcitabine, and found that it was significantly elevated in tumors exposed to TO901317 (P<0.03). Conclusions: The LXR agonist TO901317 enhances the cytotoxic effects of gemcitabine to promote tumor regression in a human xenograft model of pancreatic adenocarcinoma. Therefore, LXR agonists, such as TO901317 and oxysterols, may represent a novel strategy to target pathologic Hh signaling within both tumor cells as well as the surrounding stroma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3494. doi:1538-7445.AM2012-3494

Reversible epithelial to mesenchymal transition and acquired resistance to sunitinib in patients with renal cell carcinoma: evidence from a xenograft study

Tyrosine kinase inhibitors (TKI) targeting angiogenesis via inhibition of the vascular endothelial growth factor pathway have changed the medical management of metastatic renal cell carcinoma. Although treatment with TKIs has shown clinical benefit, these drugs will eventually fail patients. The potential mechanisms of resistance to TKIs are poorly understood. To address this question, we obtained an excisional biopsy of a skin metastasis from a patient with clear cell renal carcinoma who initially had a response to sunitinib and eventually progressed with therapy. Tumor pieces were grafted s.c. in athymic nude mice. Established xenografts were treated with sunitinib. Tumor size, microvascular density, and pericyte coverage were determined. Plasma as well as tissue levels for sunitinib were assessed. A tumor-derived cell line was established and assessed in vitro for potential direct antitumor effects of sunitinib. To our surprise, xenografts from the patient who progressed on sunitinib regained sensitivity to the drug. At a dose of 40 mg/kg, sunitinib caused regression of the subcutaneous tumors. Histology showed a marked reduction in microvascular density and pericyte dysfunction. More interestingly, histologic examination of the original skin metastasis revealed evidence of epithelial to mesenchymal transition, whereas the xenografts showed reversion to the clear cell phenotype. In vitro studies showed no inhibitory effect on tumor cell growth at pharmacologically relevant concentrations. In conclusion, the histologic examination in this xenograft study suggests that reversible epithelial to mesenchymal transition may be associated with acquired tumor resistance to TKIs in patients with clear cell renal carcinoma.

Abstract 388: Epithelial to mesenchymal transition is associated with acquired resistance to sunitinib in patients with renal cell carcinoma: evidence from a xenograft study

Purpose: Tyrosine kinase inhibitors (TKIs) targeting angiogenesis via inhibition of the vascular endothelial growth factor (VEGF) pathway have changed the medical management of metastatic renal cell carcinoma. While the treatment with TKIs has demonstrated clinical benefit these drugs will eventually fail patients. The potential mechanisms of resistance to TKIs are poorly understood. Experimental Design: To address this question we obtained an excisional biopsy of a skin metastasis from a patient with clear cell renal carcinoma who initially had a response on sunitinib and eventually progressed on therapy. Tumor pieces were grafted subcutaneously in athymic nude mice. Established xenografts were treated with sunitinib. Tumor size, microvascular density and pericyte coverage were determined. Plasma as well as tissue levels for sunitinib were assessed. A tumor derived cell line was established and assessed in vitro for a potential direct antitumor effects of sunitinib. Results: To our surprise, xenografts from the patient who progressed on sunitinib regained sensitivity to the drug. At a dose of 40 mg/kg sunitinib caused regression of the subcutaneous tumors. Histology showed a marked reduction in microvascular density and pericyte dysfunction. More interestingly, histological examination of the original skin metastasis revealed evidence of epithelial-to-mesenchymal-transition while the xenografts showed reversion to the clear cell phenotype. In vitro studies showed no inhibitory effect on tumor cell growth at pharmacologically relevant concentrations. Conclusions: The histological examination in this xenograft study suggests that reversible epithelial-to mesenchymal-transition may be associated with acquired tumor resistance to TKIs in patients with clear cell renal carcinoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 388.

A phase I study assessing the feasibility and safety of intraductal pegylated liposomal doxorubicin (PLD) in women with breast cancer

e11506

Background: Most breast cancers originate in epithelial cells lining the breast ducts. Preclinical data suggest that intraductal administration of chemotherapy including PLD decrease tumor volume, prevent the development of new lesions, and eradicate pre-malignant disease. We initiated a clinical trial to determine the feasibility, safety, and maximum tolerated dose of PLD administered into one duct of women awaiting mastectomy. Methods: Women 18 or older awaiting mastectomy for breast cancer were eligible. Preoperative chemotherapy was allowed. T4 tumors, prior breast irradiation, or surgeries that may have altered the ductal system were excluded. Nipple aspiration and ductal cannulation were completed and the first 3 women received 5 mL of intraductal dextrose. PLD was administered to subsequent participants on a dose escalation schema based on preclinical pharmacokinetic and safety data. Serial doxorubicin (Dox) and doxorubicinol (Doxol) concentrations were determined in plasma by LC/MS/MS. At mastectomy (completed at least 2 weeks after intraductal administration of PLD), blue dye was injected into the treated duct and tissue was obtained for pharmacokinetic and biomarker analysis. Results: From 2/06 to 6/08, 14 women enrolled, and 12 underwent all study procedures. All dose levels up to 10 mg PLD per one duct were completed without serious adverse events. Median pain score was 0.9 (0–2.3). Intraductal PLD resulted in a dose-dependent increase in both systemic and local exposure to dox and doxol. Neither dox nor the metabolite was detected in the contralateral breast. Systemic exposure was lower than with conventionally administered PLD. Inflammatory changes were not observed on histopathological review of mastectomy specimens. Conclusions: We have established the logistics of intraductal administration of agents in an outpatient setting and it is feasible in women with and without prior chemotherapy. Biomarker data will be completed prior to the meeting. Future studies will evaluate other agents administered to one or more ducts.

[Table: see text]

Phase I dose escalation trial of sorafenib as a single agent for adults with relapsed and refractory acute leukemias

7065

Background: Sorafenib is a multikinase inhibitor with activity against B-raf, VEGF, and FLT3. Based on preclinical activity in FLT3 mutant AML, sorafenib was studied in refractory acute leukemia. Methods: The primary objective was to determine the safety and tolerability of sorafenib in refractory acute leukemias. Secondary objectives included pharmacokinetics (PK) and pharmacodynamic (PD) effects of sorafenib on FLT3 phosphorylation. Dose escalation began at 400 mg BIDx14days per month, and proceeded through 600 mg BID x 21 days per month. Plasma concentration of sorafenib and its primary metabolite sorafenib N-oxide were measured by LC/MS//MS method. The plasma inhibitory assay was used to measure target inhibition of phosphorylated FLT3 and phosphorylated Erk. Results: Fifteen patients (13 = AML, 2 = ALL) were enrolled (ages 37–85) and treated on three dosing schedules (400 mg BID x 14 d, 400 mg BID x 21 days, 600 mg BID x 21days) of single agent sorafenib. The maximally tolerated dose was 400 mg BID x 21 days per month. Grade 3 or greater toxicities were experienced in 55% of cycles, most common grade 3 or greater toxicities being fatigue (16%) and hypokalemia (13%). No patients met criteria for complete or partial response, but 11 of 15 (73%) patients experienced stable disease as best response, with 6 showing a reduction in bone marrow blasts after only one cycle, half of who experienced a >50% reduction in bone marrow blasts. Interestingly, 2 pts with FLT3-ITD mutations both showed marrow blast response (1 pt >50%). Sorafenib resulted in sustained complete inhibition of FLT3 and Erk as demonstrated in all patients assessed (n = 11). Importantly, this inhibition was maintained throughout treatment cycle and 3/5 pts had FLT3 inhibitory activity 7 days post their last dose. Correlative studies suggest sorafenib N-oxide is an active metabolite. Conclusions: Sorafenib is a potent inhibitor of FLT3 with favorable PK and PD properties. Clinical activity as a single agent was limited to transient reductions in bone marrow blast counts and dose escalation was limited due to toxicities. Based on PK data in conjunction with standard curves for inhibition of FLT3 by sorafenib in plasma, the minimum FLT3 inhibitory dose of sorafenib is likely less than 400 mg BID.

No significant financial relationships to disclose.

Pharmacodynamic (PD) study of pre-prostatectomy rapamycin in men with advanced localized prostate cancer (PC): A DOD Prostate Cancer Clinical Trials Consortium Trial

5001

Background: Rapamycin is an orally bioavailable and generic mTOR inhibitor with an MTD of 6 mg daily and anticancer activity in solid tumors. We sought to determine the optimal biologic dose (OBD) in the pre-operative setting in men with PC. Methods: We explored the safety and PD activity of 3 and 6 mg of daily oral rapamycin for 14 days prior to radical prostatectomy (RP) in cohorts of 21 men with intermediate risk localized PC. Ten untreated control subjects were included using identical inclusion criteria. Men had Gleason >6 PC involving multiple cores. PD markers in pre-treatment prostate biopsies and RP specimens included p-S6 and p-Akt, 4EBP-1, PTEN, p27, Ki-67, and cleaved caspase-3. Tissue and whole blood sirolimus levels were measured. A Simon 2-stage design using PD efficacy (tumor S6 inhibition > 60%) was utilized. Results: 32 subjects were accrued to this 2 stage pharmacodynamic trial, including 10 control subjects. Median pre-treatment PSA was 6.4 ng/dl, age 60y, Gleason 7 in 85%. 20 accrued to the 3 mg cohort without DLT. However, 2/2 men enrolled at the 6 mg dose level experienced DLT consisting of thrombocytopenia leading to a delay in surgery (<100K) and fever with grade 3 stomatitis. AEs observed in the 3 mg cohort included stomatitis (2), rash (1), post-operative ileus (2), and mild neutropenia (2). One post-operative ileus was observed among control patients. PD studies demonstrated tumor S6 inhibition in >50% of subjects (median 60% decline, p=0.026 vs. baseline) with no negative effect on the state of Akt phosphorylation (p=0.82) or p27 levels (p=0.10). Prostate sirolimus levels (range 7.1–47.2 ng/g) were two-fold higher than whole blood concentrations (range 3.2–19.2 ng/ml). There was no effect of rapamycin on rates of post-operative wound healing or bleeding. PBMC S6 activity inhibition did not correlate with tumor S6 inhibition. Conclusions: The MTD/OBD of daily rapamycin in the pre-operative or prevention setting is 3 mg. This dose demonstrated downstream mTOR inhibition in tumor tissue and achieved adequate prostate tissue levels. Additional PD and genomic studies will be presented. Conducted through the DOD PCCTC and registered at clinicaltrials.gov as NCT00311623 .

[Table: see text]

Integrated development of s-trans, trans-farnesylthiosalicyclic acid (FTS, salirasib) in advanced pancreatic cancer

4529

Background: The Ras signaling pathway stands as a strategic target in pancreatic cancer. S-trans,trans-farnesylthiosalicyclic acid (FTS) inhibits Ras dependent cell growth by dislodging all of the isoforms of Ras from membrane binding sites. Here we studied the activity of this agent in patients with advanced pancreatic cancer. Methods: Patients with treatment naïve advanced peri-ampullary cancer were treated with gemcitabine (Gem) administered at standard dose and schedule + FTS administered orally at doses of 200–800 mg bid 21 days of a 28 day cycle. Patients were treated until progression or protocol defined DLT. Plasma samples were collected when FTS was administered alone (C1D7 or C1D22) and in combination (C1D15 or C1D8) to characterize FTS pharmacokinetics. Plasma samples were collected when Gem was administered alone (C1D1) and in combination (C1D15 or C1D8) to characterize Gem pharmacokinetics. PBMCs and tissue biopsies pre treatment and during cycle 1 were collected to characterize the effect of Gem + FTS on levels of activated Ras protein. Treatment efficacy was assessed every other cycle. Results: Thirteen patients (8 male, 5 female, ages 40 to 80, ECOG 0–1) are enrolled to date. The most common adverse events were neutropenia, anemia, abdominal cramping, elevated liver function tests and diarrhea. At the time of this analysis, the progression free survival for these 13 patients is 4.7 months with median survival of >10.8 months and 1 year survival of 50%. Conclusions: 1. Salirasib in combination with gemcitabine appears to be safe with no PK interaction. 2. Salirasib in combination with gemcitabine at doses to 800 mg b.i.d. did not reach conventional MTD, although dose related diarrhea suggests better tolerance at doses up to 600 mg b.i.d. 3. Salirasib at doses of 400 to 800 mg b.i.d. in combination with gemcitabine demonstrated a PFS, MS and 1 year survival of 4.7 months, >10.8 months and 50% respectively. 4. Salirasib mechanism of Ras inhibition is confirmed by reduction of tumor Ras in pancreatic cancer patients. 5. Salirasib warrants evaluation in a controlled study with gemcitabine in pancreatic cancer; doses of 600 or 400 mg b.i.d. are recommended.

No significant financial relationships to disclose.

Preclinical identification of biomarkers of response to mTOR inhibitors and subsequent application in a phase II trial of sirolimus in pancreatic cancer patients refractory to gemcitabine

4612

Background: Treatment for advanced pancreatic cancer refractory to gemcitabine has not been defined. We conducted an efficacy study in pancreatic cancer xenografts to identify biomarkers of response to mTOR inhibition and attempted to translate the results by conducting a phase II trial of sirolimus in this patient population. Methods: 19 direct pancreatic xenografts were treated with temsirolimus (20mg/Kg IP daily) for 28 days. Tumors were profiled with array CGH and gene expression arrays at baseline. TGI were calculated at 28 days. Patients refractory to gemcitabine were included in the clinical trial. Sirolimus was administered at 5mg/day for 28 days. Primary endpoint was 6 month survival rate (6mSR). Secondary endpoints included: baseline evaluation of AKT pathway activation, pharmacodynamic assessment of p-S6K in PBMC, pharmacokinetics and toxicity analysis. Results: In the preclinical study, mTOR sensitive tumors showed upregulation of genes involved in the renal cell cancer pathway. CGH identified focal gains in N-Ras and K-Ras and homozygous deletions of FHIT in sensitive cases. Overall, these genetic changes induced AKT pathway activation, and led us to explore high baseline p-S6K expression as a predictor of outcome in the clinical phase. Patient characteristics: Median age: 64 (39–77). 11 patients had received ≥ 2 prior lines of chemotherapy. 6mSR was 20%. 6mSR in the subgroup of patients who received rapamycin as first line chemotherapy after progression to gemcitabine was 34%. Baseline tumor p-S6K was not predictive for survival. Early pharmacodynamic changes in p-S6K in PBMC 6 hours after treatment initiation were correlated with survival (R2= 0.65). Treatment was well tolerated. The most common grade 3 adverse event was hyperglycemia in 10% of the patients. 7 (23%) patients achieved stable disease. Conclusions: Rapamycin is well tolerated in this setting. Early pharmacodynamic changes in p-S6K in PBMC were correlated with survival. Preclinical findings leading to activation of the AKT pathway in all sensitive cases warrants further validation studies. Efficacy data is limited by the selection of a heavily pretreated and poor prognosis population (DFS≤47 days).

No significant financial relationships to disclose.

A phase I study of EKB-569 in combination with capecitabine in patients with advanced colorectal cancer

PURPOSE

To determine the maximum tolerated dose (MTD), characterize the principal toxicities, and assess the pharmacokinetics of EKB-569, an oral selective irreversible inhibitor of the epidermal growth factor receptor tyrosine kinase, in combination with capecitabine in patients with advanced colorectal cancer.

EXPERIMENTAL DESIGN

Patients were treated with EKB-569 daily for 21 days and capecitabine twice daily for 14 days of a 21-day cycle. The dose levels of EKB-569 (mg/day) and capecitabine (mg/m(2) twice daily) assessed were 25/750, 50/750, 50/1,000 and 75/1,000. An expanded cohort was enrolled at the MTD to better study toxicity and efficacy. Samples of plasma were collected to characterize the pharmacokinetics of the agents. Treatment efficacy was assessed every other cycle.

RESULTS

A total of 37 patients, the majority of whom had prior chemotherapy, received a total of 163 cycles of treatment. Twenty patients were treated at the MTD, 50 mg EKB-569, daily and 1,000 mg/m(2) capecitabine twice daily. Dose-limiting toxicities were diarrhea and rash. No patients had complete or partial responses but 48% had stable disease. The conversion of capecitabine to 5-fluorouracil was higher for the combination of EKB-569 and capecitabine (321+/-151 ng*h/mL) than for capecitabine alone (176+/-62 ng*hours/mL; P=0.0037).

CONCLUSION

In advanced colorectal cancer, 50 mg EKB-569 daily can be safely combined with 1,000 mg/m(2) capecitabine twice a day. A statistically significant increase in plasma levels of 5-fluorouracil for the combination of EKB-569 and capecitabine may be due to the single-dose versus multiple-dose exposure difference, variability in exposure or a potential drug interaction.

Predicting and monitoring tumor response to epidermal growth factor receptor inhibitor gefitinib in patients with locally advanced esophageal adenocarcinoma

14112

Background: This study aimed to validate an ex vivo chemosensitivity assay to measure the pharmacodynamic effect of gefitinib on esophageal adenocarcinoma (EAC) prior to treatment with pre-operative concomitant chemoradiotherapy (CRT). Methods: A 14 day run-in period with 250 mg/day of gefitinib preceded CRT. Endoscopic biopsies (D 0 and 14) in 4 patients with T2–3N0/1M0/1a EAC were analyzed by ex vivo chemosensitivity assay. Day 0 tissue was exposed to gefitinib ex vivo, then tumor was exposed to gefitinib for 14 days in vivo (ie in the patient). Phosphorylation of the EGFR, raf/MEK/ERK and PI3/AKT pathways was measured by Western blot. Profiles were compared for correlation between ex vivo and in vivo exposure, and patterns were correlated with response to CRT. The effects were also characterized by immunohistochemistry (IHC). EGFR, K-Ras, and PI3K mutations, serum concentrations of gefitinib and PTEN status were measured as potential confounders. Results: One patient with stage T3N1 died of unexplained hemorrhage during surgery. Three had clinical and path stages of: T3N1/T0N0, T3N0/T3N0, T3N1/T2N1. Gefitinib levels were constant, confirming exposure of target tissue to the drug. Ex vivo exposure yielded four distinct pathway patterns. The exact same patterns were seen after in vivo exposure. No mutations were identified in exons 18–21 of the EGFR, exons 2/3 of K-ras or exons 9/22 of PI3K. PTEN levels were similar in all tumors. PCNA expression correlated with raf/MEK/ERK pathway inhibition, but not with inhibition of EGFR activity. IHC correlated with Western blot for expression of EGFR, and phospho- and total ERK levels. No correlation was observed between gefitinib effect and pathologic response to CRT. Conclusions: This study used a novel ex vivo chemosensitivity assay to demonstrate the activity of gefitinib to inhibit target in tumor tissue obtained from patients with EAC. The exact correlation of pre- and post-treatment profiles suggests potential use in the pre-treatment setting to predict in vivo effects of targeted therapies. This approach may facilitate the further refinement of patient selection to maximize potential benefit while sparing patients unlikely to respond to a given agent.

No significant financial relationships to disclose.

Evaluation of ON 01910.Na, a novel modulator of polo-like kinase 1 (Plk1) pathway, and development of a cyclin-B1-based predictive assay in pancreatic cancer

3569

Background: Plk1 is a key mitotic regulator of the transition through the G2/M checkpoint in the cell cycle. This work aimed to evaluate the activity of ON 01910.Na, a Plk1 pathway modulator, in in vitro and in vivo models of pancreatic cancer (PaCa) and to discover biomarkers predictive of efficacy. Methods: ON 01910.Na was tested in 12 PaCa cell lines. Studies assessing Plk1 related markers were conducted to identify biomarkers. For validation a live collection of PaCa xenografts from fresh tumor samples obtained at the time of surgical resection was used (PancXenoBank). The ex vivo assay was based on fine-needle aspirate (FNA) biopsies. Results: ON 01910.Na showed equal activity to gemcitabine against PaCa cell lines. The activity of ON 01910.Na correlated with suppression of two downstream mediators of PLK1, CDC25C and cyclin B1 (by mRNA and protein). ON 01910.Na was tested in xenografts from representative pancreatic cell lines. The selected markers were evaluated in an ex vivo assay, using intra-tumor pharmacokinetics to select the dose of the assay. Cyclin B1 mRNA evaluation yielded the most optimal combination of accuracy and reproducibility. Knockdown of cyclin B1 by siRNA had no effect per se or in the response of the resistant MiaPaca2 to either of the drugs. We next used the ex vivo assay to profile ten patient-derived cases from the PancXenoBank. Two cases were catalogued as potential responders. From each of these ten cases, a group of mice bearing at least 20 tumors received vehicle or ON 01910.Na for 28 days. There was a correlation between the ex vivo cyclin B1 assay and the sensitivity to the tested agent, as the 2 cases prospectively identified as sensitive met pre-specified criteria for response. Of the 8 tumors predicted to be resistant, only one was sensitive. In IHC testing cases showing ex vivo cyclin B1 down-regulation had also decreases in cyclin B1 protein, and there was a correlation between activity and IHC changes in cyclin B1. Conclusions: ON 01910.Na demonstrated significant activity in a preclinical model of PaCa. A rationally designed ex vivo cyclin B1-based assay not only identified cases sensitive to ON 01910.Na, but also replicated the pharmacodynamic events occurring after in vivo exposure.

No significant financial relationships to disclose.

Phase 1 pharmacokinetic and pharmacodynamic study of the histone deacetylase inhibitor MS-275 in combination with 13-cis retinoic acid in patients with advanced solid tumors

3055

Background: Preclinical studies suggest that histone deacetylase (HDAC) inhibitors may restore tumor sensitivity to retinoids. The objective of this study was to determine the maximum-tolerated dose (MTD), the dose-limiting toxicity (DLT), and the pharmacokinetic (PK)/pharmacodynamic (PD) profiles of the HDAC inhibitor MS-275 in combination with 13-cis retinoic acid (CRA). Methods: Patients (pts) with advanced solid tumors were treated with MS-275 orally once weekly and CRA orally twice daily x 3 weeks every 4 weeks. The starting dose for MS-275 was 4 mg/m2 and the dose was escalated based on toxicity assessments. The fixed dose for CRA was 1 mg/kg/day. PK concentrations of MS-275 and CRA were determined by LC/MS/MS. Western Blot analysis on peripheral-blood mononuclear cells (PBMCs) and tumor samples (when feasible) were performed to evaluate target inhibition. Results: To date thirteen pts have been enrolled. Tumor types include prostate (4 pts), bladder and renal cell (2 pts), and others. The MTD was exceeded at the 5 mg/m2 dose level (G3 hyponatremia, neutropenia and anemia). Fatigue (G1 or G2) is a common side effect. MS-275 peak concentrations were 141.6±75.7ng/mL at 4mg/m2 and 139.5±30.9 ng/mL at 5mg/m2. MS-275 half-life and clearance were 108.2±47.9h and 9.4±6.0L/h/m2, which is consistent with prior reports for MS-275 as single agent. Median CRA steady-state trough levels were 182.4 ng/mL. The MTD was 4 mg/m2 MS-275 and 1 mg/kg CRA. Five pts remained on treatment for ≥ 4 months including pts with prostate cancer (3), pancreatic cancer (6 months) and a pt with renal cell carcinoma (12 months) who presented a partial response in the lungs. Histones isolated from PBMCs showed transient but consistent protein acetylation post-therapy. Tumor biopsy of a liver lesion from prostate carcinoma revealed post-therapy induced histone acetylation and decreased phosphorylated ERK and STAT3 protein expression consistent with HDAC inhibitory activity. Conclusions: Combination of MS-275 with CRA is reasonably well tolerated and 4 mg/m2 is the Phase II recommended dose for MS-275 in combination with CRA. Tumor response and PD data suggest clinical and biological activity for this combination strategy.

[Table: see text]