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Renin-angiotensin system (RAS) antagonists are recommended for people with diabetes and hypertension or with elevated urinary albumin excretion. RAS antagonists are beneficial for some, yet clinically inappropriate for others. The percentage of patients for whom RASs are clinically inappropriate has not been compared across health plans.To (a) identify reasons why RAS therapy was not recommended and (b) compare exception percentages between health plans.This retrospective, cross-sectional analysis included Medicare Part D beneficiaries with diabetes, enrolled in health plans (n = 96) participating in a university-based medication therapy management (MTM) program between January 1 and December 31, 2013. The MTM program evaluated patient eligibility for RAS therapy via (1) a clinically derived software system assessing demographics and medication history, and (2) telepharmacist-delivered medication reviews. The MTM program database calculated the number of patients with diabetes and percentage of RAS therapy exceptions.An average of 55% of patients with diabetes qualified for MTM (range: 19%-88%). Of the 218,589 eligible, 94,359 had 1 or more reasons contraindicating RAS therapy (exception). For an average of 29% of patients, it was inappropriate to recommend the addition of an RAS antagonist; the overall exception rate ranged from 3% to 83%, suggesting a wide variation of exception rates for all health plans.A substantial difference existed across health plans where RAS therapy was considered clinically inappropriate to recommend for patients with diabetes. Future research must examine variations in therapy exceptions to understand the effect of encouraging broad-population RAS antagonist use.SinfoníaRx provided funding for this project. Wild, Boesen, and Werner are employed by SinfoniaRx, which provided grant funding to the University of Arizona College of Pharmacy for the conduct of this study. This project was presented at the AMCP 27th Annual Meeting and Expo; April 8-10, 2015; San Diego, CA.

6029 Background: The absence of infiltrating antigen-specific CD8+ T-cells at baseline is associated with low response rates to PD-1 blockade. SCCHN tumors often exclude effector T cells, and 2nd line response rates are low (13-18%). Highly immunogenic, antigen specific antitumor vaccines may expand intratumoral CD8+ T cells, potentially increasing durable response rates to PD-1 blockade. SNS-301 is a first-in-class, bacteriophage-based immune activating agent targeting human aspartate β-hydroxylase (ASPH), a tumor associated antigen overexpressed in multiple tumor types. SNS-301 is a self-adjuvanted vaccine consisting of λ-bacteriophage engineered to express an immunogenic fragment of ASPH fused to the phage gpD coat protein. The study objectives are to evaluate safety, immunogenicity and preliminary efficacy of SNS-301 added to pembrolizumab in patients (pts) not achieving tumor reductions on PD-1 blockade alone. Methods: Intradermal SNS-301 was combined with pembrolizumab in pts with locally advanced unresectable (LA) or metastatic/recurrent (met) SCCHN with a best response of stable disease (SD) or unconfirmed progressive disease (uPD) on ongoing PD-1 blockade > 12 weeks. Pts provided pre and on-treatment biopsies to characterize the tumor microenvironment using Nanostring and multiplex immunohistochemistry (mIHC). Blood samples were collected to evaluate B and T cell responses using ELISA/ELISPOT assays. Results: As of February 4, 2021, 13 pts were enrolled. Median duration of PD-1 blockade was 48 weeks (range 14-114) at study entry. There were no DLTs & mostly Grade 1-2 unrelated adverse events. Only two related Grade 3 events were reported: rash & dehydration (also a serious adverse event). Ten pts were evaluable for efficacy: 1 pt with PD-L1 negative (neg) disease & SD on pembrolizumab monotherapy achieved a partial response (PR; -52% at 8 months), 4 pts achieved SD & 5 pts had progressive disease. Two of the pts with SD had long-lasting duration (8 & 10 months) of which the latter had PD-L1 neg disease. One pt with uPD at enrollment achieved SD for 4 months. Analyses of pre- & on-treatment biopsies from the PR pt demonstrated an increase in infiltrating CD8+ T cells, PD-L1 expression & PD-1/PD-L1 proximity measures. Nanostring analysis demonstrated increased gene expression signatures for immune cells in the PR pt that was concordant with the mIHC & clinical outcome. Conclusions: The combination of SNS-301 and pembrolizumab was well-tolerated and resulted in encouraging clinical efficacy in pts not expected to respond to PD-1 blockade alone. Translational data suggest cellular response to SNS-301 and transformation of a poorly inflamed tumor to an immunologically active tumor in a responding pt (PR). Based on these data, an additional cohort will start enrolling PD-1 blockade naïve pts with LA/met SCHNN in the front-line setting. Clinical trial information: NCT04034225.

Lessons LearnedVandetanib at a dose of 300 mg orally every day plus bortezomib 1.3 mg/m2 intravenously on days 1, 4, 8, and 11 could be administered safely. Assessing outcomes in 17 patients with medullary thyroid cancer, investigators considered the combination to be more difficult to administer than single-agent vandetanib and that achieving better outcomes was unlikely. Consequently, a planned phase II study was terminated early.BackgroundThe proto-oncogene RET (REarranged during Transfection) has a critical role in the pathogenesis of medullary thyroid cancer (MTC). Vandetanib (V), a multitargeted tyrosine kinase inhibitor approved for the treatment of MTC, is thought to inhibit RET in MTC. Supported by preclinical studies demonstrating that bortezomib (B) administration lowered RET mRNA and protein levels, we conducted a phase I study in advanced solid tumors of vandetanib in combination with bortezomib. The goal was to establish an RP2D (recommended phase II dose) for the combination of vandetanib plus bortezomib, a regimen envisioned as a dual strategy for targeting RET in MTC.MethodsPatients with advanced solid tumors were treated with escalating doses of bortezomib or vandetanib to assess the safety and tolerability of daily oral vandetanib and intravenous (IV) bortezomib administered on days 1, 4, 8, and 11 of a 28-day cycle. Intrapatient dose escalation was allowed.ResultsTwenty-two patients were enrolled and received escalating mg/m2 bortezomib and mg vandetanib (number of patients) at initial doses of 1 and 100 (3), 1.3 and 100 (6), 1.3 and 200 (6), and 1.3 and 300 (7), respectively. Patients received a median of four cycles of bortezomib/vandetanib (range: 1–10), with 13 patients escalating to 1.3/200 and 10 to 1.3/300. G3 toxicities occurring in more than one patient included hypertension (24%), fatigue (19%), thrombocytopenia (10%), diarrhea (10%), and arthralgia (10%). There were no drug-related G4/5 toxicities. There was one dose-limiting toxicity, G3 thrombocytopenia, at bortezomib/vandetanib doses of 1.3/200 in cycle 2 that resolved without intervention. Four patients with a diagnosis of MTC (27%) had a partial response (PR).ConclusionThe MTD of the combination was established as bortezomib, 1.3 mg/m2 IV days 1, 4, 8, and 11 with vandetanib 300 mg p.o. daily. RECIST responses were observed in patients with a diagnosis of MTC.

National guidelines and initiatives have promoted the use of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) for patients with diabetes. The University of Arizona Medication Management Center (UA-MMC) is contracted by Medicare health plans, pharmacy benefit managers (PBMs), and multiple commercial health insurance plans to provide medication therapy management (MTM) services for plan members. As part of the MTM program, recommendations have been made for those patients who may benefit from the addition of an ACEI/ARB. Although the intervention benefits and guidelines for using ACEIs/ARBs are clear, real-world evidence is needed to understand and potentially increase uptake of guideline interventions among eligible patients.To (a) identify patient characteristics that predict acceptance of guideline recommendations to add ACEI/ARB medications to diabetic treatment via MTM services and (b) examine how well different case characteristics (i.e., patient age and sex, type and number of recommendation attempts, type of health care plan) predict the odds of adding ACEI/ARB medications to diabetic regimens when recommended through an MTM call center.This was a retrospective analysis of secondary data provided by the UA-MMC. The de-identified national data included adult plan members with diabetes who the UA-MMC recommended adding an ACEI/ARB prescription based on 2012 national guidelines. The UA-MMC made recommendations by either patient letters, patient phone calls, physician faxes, or any combination thereof. We conducted a binary logistic regression analysis to assess the impact of case characteristics on the likelihood of accepting recommendations to add ACEI/ARB medications. The outcome variable was recommendation acceptance (yes/no), defined as new prescription claims for an ACEI/ARB within 120 days following the recommendation. Five predictor variables were assessed: (1) patient's age quartile; (2) method of communicating recommendations (letter, phone call, fax, or some combination thereof); (3) whether recommendations were made once or twice on separate dates; (4) patient's sex; and (5) type of health care plan.Recommendations were made for 31,495 members of health plans or PBMs that contracted with the UA-MMC. Patients' ages ranged from 19-90 (Mean =72.01; SD =10.21), with females comprising 56% of the sample. The recommendation to add ACEI/ARB medications was accepted for 14.5% (4,559) of patients. In most cases (73%), recommendations occurred via a letter to patients together with a fax to their providers. The fitted model, containing 3 predictor variables (age quartile, type of contact to communicate the recommendations, and whether recommendation contacts were made twice), was statistically significant, χ(2) (10; N = 31,495) = 112.82 (P0.001), indicating that the model was able to distinguish between those who did and did not accept UA-MMC's recommendations to add ACEI/ARB medications. The likelihood of recommendation acceptance decreased as patient age increased compared with patients in the first age quartile (ages 19-67; P ≤ 0.005 at all levels). Compared with sending only a provider fax, patients who received all 3 types of contact (provider fax with patient phone call and letter) were estimated to be 1.34 times more likely (34% increase) to have recommendation acceptance ( P = 0.004; 95% CI = 1.10-1.63). Similarly, patients who received only letters were also 1.32 times more likely (32% increase) than provider faxes alone to result in recommendation acceptance ( P = 0.003; 95% CI = 1.10-1.59). Patients for whom recommendations were made twice were less likely to have recommendation acceptance than for those contacted once, controlling for all other predictor variables in the model ( P0.001; OR = 0.77; 95% CI = 0.69-0.86).Recommendations to add an ACEI/ARB to diabetic regimens are more likely to be accepted for younger patients and those who receive recommendations through all 3 communication types (provider fax combined with patient phone call and letter) or just letters than provider faxes alone. Further research is needed to understand why prescribers are not accepting MTM recommendations.

The incorporation of electronic circuitry into additively manufactured thermoplastic parts is a highly desirable innovation enabler. Applications include embedding signal traces into custom air or ground vehicle components, creation of complex interconnect devices exploiting the design freedom of 3D printers, or as a way to create various grounding, shielding, sensing or antenna patterns on custom structures. Stratasys has explored multiple approaches for creating selective metallization on 3D printed plastic parts. Earlier publications [1] described evaluations of metal-based ink deposition methods such as ink jet and aerosol jet. More recently we have explored the use of Laser Direct Structuring, (LDS) thermoplastic resins in our 3D printers. With LDS technology, parts are selectively metallized after 3D part build through a laser imaging and electroless plating process. Finally, some early feasibility work has been attempted using inherently electrically conductive materials. In this paper, the various methods evaluated for integration of metal traces with 3D parts will be discussed, along with part examples and performance comparisons.

Background Anaplastic thyroid cancer (ATC) is an aggressive neoplasm for which a paucity of data exist about the relative role of operative procedures in disease management. Methods The FACT trial was a randomized, controlled phase 2/3 trial assessing the safety and efficacy of carboplatin/paclitaxel with CA4P (experimental arm) or without CA4P (control arm) in ATC, 2007-11. Patients were permitted to have had an operation before enrollment, which was stratified on the basis of exposure to operation. A subpopulation of patients who had a cancer-related operation (thyroidectomy) was compared with those who did not, and 1-year and median survival were estimated. Results A total of 80 patients were enrolled; 55% had undergone a cancer-related operation, of whom 70% had near-total/total thyroidectomy. Baseline characteristics for operative and nonoperative patients were not substantially different. Median survival for patients who had cancer-related operation was 8.2 months in the CA4P arm versus 4.0 months in the control arm, resulting in a hazard ratio of 0.66 ( P = .25) and a suggested associated reduction in risk of death of 35%. 1-year survival was 33.3% in the CA4P arm versus 7.7% in the control arm. Conclusion In this largest prospective study ever conducted in ATC, thyroidectomy followed by CA4P combination regimen showed a nonsignificant trend toward improvement in patient survival.

6077Background: Long-term toxicity is a concern in patients undergoing head and neck re-irradiation. Durable local control is achieved in majority of patients in combination with chemotherapy and s...

Anaplastic thyroid cancer (ATC), a rare highly vascularized tumor, has a dismal outcome. We conducted an open-label study of doublet carboplatin/paclitaxel chemotherapy with or without fosbretabulin in patients with ATC.Patients were randomly assigned in a 2:1 ratio to 6 cycles of paclitaxel 200 mg/m(2) followed by carboplatin AUC 6 on day 1 every 3 weeks (CP), or these drugs were given on day 2 after fosbretabulin 60 mg/m(2) (CP/fosbretabulin) on days 1, 8 and 15. After 6 cycles, patients on the fosbretabulin arm without progression could continue to receive fosbretabulin on days 1 and 8 of a 3-week schedule until progression. The primary end point was overall survival (OS).Eighty patients were assigned (planned, 180) when enrollment was stopped due to rarity of disease and very low accrual. Median OS was 5.2 months [95% confidence interval (CI) 3.1, 9.0] for the CP/fosbretabulin arm (n=55; hazard ratio 0.73 [95% CI 0.44, 1.21]) and 4.0 months [95% CI 2.8, 6.2] for the CP arm (n=25; p=0.22 [log rank test]). One-year survival for CP/fosbretabulin versus CP was 26% versus 9%, respectively. There was no significant difference in progression-free survival between the two arms. Grade 1-2 hypertension and grade 3-4 neutropenia were more common with CP/fosbretabulin. There were no significant adverse cardiovascular side effects.Although the study did not meet statistical significance in improvement in OS with the addition of fosbretabulin to carboplatin/paclitaxel, it represents the largest prospective randomized trial ever conducted in ATC. The regimen is well tolerated, with AEs and deaths primarily related to ATC and disease progression.

A phase 1 study was initiated to determine the safety, potential effectiveness, and maximal tolerated dose and recommended phase 2 dose of efatutazone and paclitaxel in anaplastic thyroid cancer.Patients received efatutazone (0.15, 0.3, or 0.5 mg) orally twice daily and then paclitaxel every 3 weeks. Patient tolerance and outcomes were assessed, as were serum efatutazone pharmacokinetics.Ten of 15 patients were women. Median age was 59 years. Seven patients received 0.15 mg of efatutazone, 6 patients received 0.3 mg, and 2 patients received 0.5 mg. One patient receiving 0.3 mg of efatutazone had a partial response from day 69 to day 175; 7 patients attained stable disease. Median times to progression were 48 and 68 days in patients receiving 0.15 mg of efatutazone and 0.3 mg of efatutazone, respectively; corresponding median survival was 98 vs 138 days. The median peak efatutazone blood level was 8.6 ng/mL for 0.15-mg dosing vs 22.0 ng/mL for 0.3-mg twice daily dosing. Ten patients had grade 3 or greater adverse events (Common Terminology Criteria for Adverse Events), with 2 of these (anemia and edema) related to efatutazone. Thirteen events of edema were reported in 8 patients, with 2 of grade 3 or greater. Eight patients had ≥1 serious adverse event, with 1 of these (anemia) attributed to efatutazone and 1 (anaphylactic reaction) related to paclitaxel. The maximal tolerated dose was not achieved. Angiopoietin-like 4 was induced by efatutazone in tissue biopsy samples of 2 patients.Efatutazone and paclitaxel in combination were safe and tolerated and had biologic activity.

This article demonstrates how the four core standards for the nurse consultant role have been developed and applied in the field of rheumatology. The authors suggest that the standards: expert practice, leadership and service redesign, research and education, are relevant for consultant nurses in all specialties. The standards can be used by other nurse consultants to benchmark their practice.

TPS3127 Background: Saccharomyces cerevisiae has been genetically modified to express CEA protein and developed under a CRADA with GlobeImmune/NCI as a heat-killed immune-stimulating, therapeutic cancer vaccine (GI-6207). A phase I study with GI-6207 demonstrated safety, biomarker stabilization and enhanced immune response in some patients. CEA is over-expressed in multiple malignancies, including medullary thyroid cancer (MTC). Two therapies recently approved by the FDA for metastatic MTC (vandetanib, cabozantinib) come with toxicity and should be reserved for symptomatic/progressive disease. However, a large population of asymptomatic MTC patients has small tumor burden and/or disease that is more indolent. The standard management of these patients is observation. Preliminary data suggest that tumor growth measured by the rate of CEA and calcitonin increase can be quantified in a 3-6 months. Retrospective data from prostate cancer studies suggest vaccines can alter growth rates within 3-4 months. We hypothesize that GI-6207 can alter tumor growth rates in MTC and impact long-term outcome. Methods: A phase II study will evaluate the effect of GI-6207 onthe rates ofincrease in calcitonin in metastatic MTC. 34 patients with minimally symptomatic, radiographically evaluable, metastatic MTC will be randomized 1:1. Arm A will receive vaccine for a year from the time of enrollment. Arm B will receive vaccine after 6 months of surveillance. GI-6207 will be administered subcutaneously at 4 sites (10 yeast units/site), every 2 weeks for 3 months, then monthly up to 1 year. The primary endpoint will compare the effect of GI-6207 on calcitonin kinetics between the vaccine and surveillance arms in the first 6 months. Secondary endpoints include immunologic responses (including antigen-specific T cell responses), objective responses, time to progression, and changes in CEA kinetics. If this trial can prospectively demonstrate that vaccines can alter tumor growth rates, and if such changes are associated with clinical outcomes, then changes in tumor growth rates may become a clinical metric to evaluate vaccine efficacy in MTC and other populations.

6074 Background: Anaplastic thyroid cancer (ATC) is one of the most aggressive of all solid tumors, with a median survival of 3-5 months. Chemotherapy has not impacted local control or survival. Crolibulin (CRO) is a microtubule destabilizing agent that disrupts vascular endothelial cells, and in turn, blood flow to the tumor. Preclinical studies showed synergism with cisplatin (CIS). The phase I portion of this phase I/II study, designed to assess the safety and tolerance of CRO and CIS in patients with solid tumors, has completed accrual. Methods: Patients with advanced solid tumors, ECOG ≤ 1, and adequate organ function were treated on a dose escalation schema with CIS (75-100 mg/m2) IV day 1 and CRO (13-20 mg/m2) IV days 1, 2, 3 (21-day cycles). CIS and CRO were continued until unacceptable toxicity or progressive disease (PD), with an option to continue CRO alone if toxicity was CIS-related. Results: Between Jan 2011 and Jan 2013, 21 patients were enrolled and assigned CIS/CRO (mg/m2) at 75/13 (6), 75/20 (3), and 100/20 (12). Diagnoses were as follows: ATC (16), urothelial carcinoma (2), prostate carcinoma (2) and mesothelioma (1). Patients received a median of 2 cycles of CIS/CRO (range: 1-6). Presently, four remain on CIS/CRO and one on CRO alone. The most common grade (G) 3 toxicities were: lymphopenia (33%), hyponatremia (29%), anemia (19%), hypertension during infusion (14%), and hypophosphatemia (9%). There were two G4 toxicities: elevated lipase and thrombocytopenia; and one G5 toxicity of laryngeal hemorrhage related to tumor erosion. There were two dose-limiting toxicities: G3 pancreatitis at dose level (DL) 1 and laryngeal hemorrhage at DL3. Eight ATC patients were treated at DL3. Of these, one (13%) had RECIST 1.1 complete response (CR) and one (13%) had stable disease (SD). Three (38%) had PD, and three are not yet evaluable. The CR has been on study for > 12 months and remains on CRO alone. Conclusions: CIS plus CRO deserves further evaluation as a regimen for ATC. The MTD of CIS/CRO is 100 mg/m2 IV day 1 and 20mg/m2 IV days 1, 2, 3 every 21 days. This combination is well tolerated, with toxicity primarily related to CIS. The phase II portion of this trial will compare CIS/CRO versus CIS in ATC patients. Clinical trial information: NCT01240590.

5565 Background: Vandetanib (V), a multi-targeted kinase inhibitor, is effective in the treatment of metastatic medullary thyroid cancer (MTC). Bortezomib (B), a proteosome inhibitor, is approved f...

5502 Background: CA4P, a vascular disrupting agent (VDA), has shown clinical activity as monotherapy in patients with ATC. Results include a durable CR in a phase I trial and a median survival of 4.7 months with 34% of patients alive at 6 months and 23% of patients alive at 1-year in a Phase 2 trial. Interim results previously presented from this phase II/III study evaluating CA4P in combination with carboplatin (C) + paclitaxel (P) in patients with ATC suggested a survival benefit with the combination therapy. Final survival and safety data are now available. Methods: This is a multicenter, open-label, 2:1 randomized trial for patients with histologically confirmed ATC. 80 out of 180 planned patients were randomized to receive up to 6 cycles of C + P with CA4P (CA4P Arm) or without CA4P (Control Arm). The targeted sample size of 180 patients was not reached due to slow enrollment. After 6 cycles of therapy, patients on the CA4P Arm without progression could continue to receive CA4P until disease progress...

Background: Stage IVC (metastatic) anaplastic thyroid cancer (ATC) has a median overall survival (OS) of only 1.9 months. Single agent paclitaxel has modest activity in ATC. In pre-clinical studies, CS-7017 inhibited ATC proliferation through a novel mechanism–activation of PPAR-γ, followed by sequential upregulation of RhoB, then p21. Moreover, CS-7017 augmented the proapoptotic effects of paclitaxel. Based on these results, a multicenter study was conducted to determine if CS-7017+paclitaxel might prove safe and effective in advanced ATC. Design: A Phase 1 study was conducted to determine the Phase 2 dose. In Phase 1, patients received CS-7017 orally BID for one week (run-in phase), followed by a 3 h iv infusion of paclitaxel (175 mg/m2) every 3 weeks in combination with BID CS-7017. CS-7017 doses were escalated (0.15, 0.3, or 0.5 mg). Tissue biopsies were obtained at baseline and at one and three weeks for immunohistochemistry of PPAR-γ responsive proteins; serum CS-7017 PK studies were also performed. Results: Nineteen patients were enrolled, but 4 were not dosed (3 due to progression, 1 ineligible). Seven participated in CS-7017 dose levels 1a/1b (0.15 mg BID), six in dose level 2 (0.3 mg BID), and two in dose level 3 (run-in phase only–0.5 mg BID). Demographics: Of the 15 treated patients, 10 (67%) were women. Median age was 59 years (range: 43-82) Efficacy: Of 15 patients receiving drug, one had a confirmed partial response (PR) lasting from Day 69 to Day 175, and eight had stable disease (SD) as their best response. Median Time to Progression in 7 patients at Dose Level 1 was 49 days, but 70 days in Dose Level 2 (43% prolongation); corresponding median survival was 99 (0.15 mg BID) vs. 140 days (0.3 mg BID, 42% increase). Median peak CS-7017 blood level was 8.6 ng/mL (range: 5.1 to 13.7) for Level 1 and 22.0 ng/mL (17.0 to 31.5) for Dose Level 2. Adverse Events: Ten patients had AEs ≥ Grade 3, with two (anemia and localized edema) related to CS-7017. Thirteen events of fluid retention/edema were reported in 8 patients, with only 2 events of CTCAE grade ≥ 3. Eight patients had ≥ one SAE, with one (anemia) due to CS-7017. One SAE (anaphylactic reaction) was related to paclitaxel. No dose limiting toxicity was observed. Immunohistochemistry: Biopsies were available on 7 patients. PPAR-γ, RXR-α, RhoB were present in all; Angiopoietin-like 4 was induced by CS-7017. Conclusions: Combination therapy with CS-7017 and paclitaxel was tolerated and has biologic activity in patients with metastatic anaplastic thyroid carcinoma, with initial exploratory data suggesting a dose-dependent improvement in time to progression and survival in response to escalating CS-7017 dosage. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1278. doi:10.1158/1538-7445.AM2011-1278

Medullary thyroid carcinoma (MTC), a neuro-endocrine cancer of parafollicular C-cells accounts for 4-10% of all thyroid cancers and has low response rates to “cytotoxic chemotherapy”. The RET proto-oncogene encodes the RET (Rearranged during Transfection) transmembrane tyrosine kinase (TK) receptor, a pivotal player and a logical target for treatment of MTC. While trials with vandetanib (V) a RET TK inhibitor (TKI) in patients with MTC have been promising, we recognized a TKI is unlikely to have maximum benefit administered alone. We sought to combine V + a drug with a broad activity profile and no overlapping toxicities. Recognizing the failure of traditional “cytotoxic” agents we investigated the proteasome (Pr) inhibitor, bortezomib (B) not yet explored clinically in MTC. Initial experiments using TT MTC cells with a mutant C634W RET, found V + B non-antagonistic in cytotoxicity assays, and V showed decreased phospho-RET expression in TT cells with 0.5 or 1 µM in 1.5h. But while V did not change RET protein levels, B decreased RET protein 7 fold and secondarily phospho-RET levels. That this was secondary to Pr inhibition and not unique to B was confirmed by treating TT cells 6h or 24h with three other Pr inhibitors – epoxomycin, lactacystin or MG132. We observed 5-9 fold decreases in RET protein, which followed a time course and a dose response, with greater reduction at 24h than at 6h. To assess if the decrease in RET protein was due to decreased RET mRNA levels, we assessed RET mRNA expression and were surprised to find a 4-9 fold decrease with Pr inhibitors. Since Pr inhibitors reduced RET by reducing mRNA levels, and reasoning this would provide an alternate strategy to impact RET function, we studied the effect of three HDAC inhibitors on RET mRNA and protein expression. Treatment of TT cells with vorinostat, belinostat, or romidepsin (R) decreased RET mRNA 3-4 fold at 24h and protein levels 4 and 7-14 fold, at 24 and 48h respectively. Furthermore B + R had greater impact than either drug separately, depressing RET protein in TT cells an additional 2-3 fold to levels 4-12 fold less than that in untreated cells, suggesting mechanisms whereby Pr and HDAC inhibitors reduce mRNA levels might differ. We have pursued the latter by examining mRNA and protein levels of 3 candidate transcription factors identified in a literature search. To date we have shown TTF1 and E2F1 mRNA levels are decreased 4-58 fold by both Pr and HDAC inhibitors whereas EGR1 levels only fall with Pr inhibitors. siRNA studies that modulate transcription factor levels will clarify their possible roles in the Pr and HDAC inhibitor drug effects and help elucidate whether these inhibitors, either alone or in combination, can prove useful in MTC therapy by reducing the crucial RET TK. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4547. doi:10.1158/1538-7445.AM2011-4547