The expression and function of the GH receptor is critical for the actions of pituitary GH in the intact animal. The role of systemic factors in the reduced expression of the GH receptor and consequent GH insensitivity in pathological states such as sepsis, malnutrition, and poorly controlled diabetes mellitus is unclear. In the current study, we demonstrate that saturated (palmitic and myristic; 50 microM) fatty acids (FA) inhibit activity of the promoter of the major (L2) transcript of the GH receptor gene; unsaturated (oleic and linoleic) FA (200 microM) do not alter activity of the promoter. Comparable effects with palmitic acid and the nonmetabolizable analog bromo-palmitic acid, and failure of triacsin C to abrogate palmitic acids effects on GH receptor expression indicate that this effect is due to direct action(s) of FA. Palmitic acid, but not the unsaturated FA linoleic acid, decreased steady-state levels of endogenous L2 mRNA and GHR protein in 3T3-L1 preadipocytes. The effect of FA was localized to two cis elements located approximately 600 bp apart on the L2 promoter. EMSA and chromatin immunoprecipitation assays established that both these cis elements bind the Krüppel-type zinc finger transcription factor, ZBP-89. Ectopic expression of ZBP-89 amplified the inhibitory effect of FA on L2 promoter activity and on steady-state levels of endogenous L2 mRNA in 3T3-L1 preadipocytes. Mutational analyses of the two ZBP-89 binding sites revealed that both the sites are essential for palmitic acid's inhibitory effect on the L2 promoter and for the enhancing effect of ZBP-89 on palmitic acid-induced inhibition of the L2 promoter. Our results establish a molecular basis for FA-induced inhibition of GH receptor gene expression in the pathogenesis of acquired GH insensitivity in pathological states such as poorly controlled diabetes mellitus and small for gestational age.

Introduction-Sepsis is associated with growth hormone (GH) insensitivity and in the intact animal the major surface component of the bacterial cell wall, lipopolysaccharide (LPS), inhibits GH receptor (GHR) gene expression. The prevailing explanation for LPS-induced effects on the GHR promoter is that this effect is indirect via generation of cytokines. Our recent studies demonstrate that saturated free fatty acids (FFAs) inhibit the activity of the murine GHR promoter. Saturated FFAs are an essential component of the lipid A moiety of LPS required for biological activity of LPS.

TPS215 Background: HER2 is expressed above normal levels by many cancers, including a range of gastrointestinal tumors. While HER2 can contribute to tumor growth and survival even when expressed at low levels, antibody-based HER2 targeted therapy has shown efficacy only in breast (trastuzumab [T], pertuzumab [P]) or gastric cancers (T) with the highest levels of HER2 expression or gene amplification. Therefore, there remains significant medical need, particularly for cancers with lower HER2 levels or more heterogeneous patterns of expression. ZW25 is a novel humanized bispecific antibody directed against two distinct epitopes of HER2. The unique structure of ZW25 leads to greater cell decoration and receptor internalization than T, even in the setting of low levels of HER2 expression. In preclinical models, ZW25 has demonstrated greater activity than T in both HER2 high and HER2 low-expressing cancers, including gastric cancer. This first-in-human study will evaluate the safety and preliminary anti-tumor activity of ZW25 in patients with advanced HER2-expressing cancers. Methods: This is a 2-part Phase 1 study utilizing 3+3 dose escalation (Part 1) and expansion cohorts (Part 2) to evaluate the MTD, safety, PK, and anti-tumor activity of ZW25 IV once per week in patients with locally advanced, unresectable and/or metastatic HER2-expressing cancers. Eligibility requirements include any HER2 1+, 2+, or 3+ cancer (Part1) or 2+/FISH negative breast or gastric cancer (Part 2) that has progressed after all approved therapies; ECOG PS ≤ 1; normal left ventricular function; and measurable disease per RECIST 1.1 (Part 2). Assessments include collection of adverse events and laboratory abnormalities, tumor response per RECIST 1.1 and exploratory response biomarkers as well as PET. Recruitment is ongoing at 3 centers in the United States. Clinical trial information: NCT02892123.

1035 Background: The HER2 receptor is expressed across a range of cancers (ca) although expression and heterogeneity vary greatly within and between tumors. FDA approved HER2-targeted therapies (tx) have shown clinical benefit only in HER2 high (IHC3+ or IHC2+/FISH+) breast and gastric ca. ZW25, built on the Azymetric™ platform which utilizes unique Fc mutations to create IgG1-like bispecific antibodies, binds to the same extracellular domains of HER2 as trastuzumab (T) and pertuzumab (P) with increased binding and internalization compared to T alone. In preclinical studies ZW25 was well tolerated and active in models of HER2 low to high ca. Methods: Eligible pts (HER2 IHC 1-3+, progression after standard of care (SOC) tx, normal LVEF) were enrolled in a 3+3 dose escalation study of ZW25 (5, 10 or 15 mg/kg) IV weekly in 4 week cycles. Assessments included adverse events (AEs), LVEF, tumor response and PK. Results: 9 pts have received ZW25 at 5 (n = 3) or 10 mg/kg (n = 6); 15 mg/kg is ongoing. All pts were HER2 high (breast = 4; gastric/GEJ = 4; adnexal = 1). Prior tx included T in all pts; P and T-DM1 in 4 and lapatinib (L) in 3 of 4 breast pts. The most common AEs (all Gr 1/2) were infusion reaction (IR) (5/9), diarrhea (4/9), and fatigue (3/9), with no DLTs and one related Gr 3 AE of hypophosphatemia. The IRs occurred only with 1st dose and did not recur with prophylactic tx (primarily acetaminophen and diphenhydramine; steroids included for 2 pts). At 5 mg/kg, peak drug levels after C1D1 = ~100 ug/ml, accumulating ~50% higher by dose 4. Best response in 8 pts (1 too early): 2 PR (both breast ca with prior T, P, T-DM1, and L; 10 mg/kg, 55% and 33% target lesion decrease, respectively, after 2 cycles), 1 SD (breast ca, 5 mg/kg, ongoing after 4 cycles), and 5 PD. 5 pts currently active; includes 1 gastric pt (10 mg/kg) with PD (new nodal lesions) and clinical benefit with decrease in target lesions and CEA (33 to 1.5 ng/ml). Conclusions: ZW25 has been well tolerated with promising anti-tumor activity in pts with HER2-expressing ca progressing after SOC therapy. These early signs of activity support the therapeutic potential for bispecific antibodies using the Azymetric platform. Development of ZW25 is ongoing, including in lower HER2-expressing ca. Clinical trial information: NCT02892123.

Background: HER2 is expressed on many cancers (ca) at varying levels. ZW25, a novel bispecific antibody, targets the same HER2 domains as trastuzumab (T) and