Characterization of the pixB gene in Xenorhabdus nematophila and discovery of a new gene family

Xenorhabdus nematophila are Gram-negative bacteria that engage in mutualistic associations with entomopathogenic nematodes. To reproduce, the nematodes invade insects and release X. nematophila into the haemolymph where it functions as an insect pathogen. In complex medium, X. nematophila cells produce two distinct types of intracellular crystalline inclusions, one composed of the methionine-rich PixA protein and the other composed of the PixB protein. Here we show that PixB crystalline inclusions were neither apparent in X. nematophila cells grown in medium that mimics insect haemolymph (Grace's medium) nor in cells grown directly in the insect haemocoel. The identified pixB gene was regulated by a conserved σ70 promoter while the pixA promoter was less well conserved. Expression of pixA and pixB under biological conditions was analysed using GFP promoter reporters. Microplate fluorescence detection and flow cytometry analyses revealed that pixB was expressed at high levels in Grace's medium and in insect haemolymph and at lower levels in complex medium, while pixA was expressed at lower levels under all conditions. Although pixB was highly expressed in Grace's medium, PixB crystalline inclusions were not present, suggesting that under biological conditions PixB production may be controlled post-transcriptionally. Although a pixB-minus strain was constructed, the function of PixB remains unresolved. The pixB gene was present in few Xenorhabdus species and pixB-type genes were identified in some Proteobacteria and Gram-positive species, while pixA was only present in Xenorhabdus species. Two conserved sequences were identified in PixB-type proteins that characterize this previously unrecognized gene family.

Abstract P5-20-04: Safety of adjuvant treatment with pertuzumab plus trastuzumab after neoadjuvant anthracycline-based chemotherapy in patients with HER2-positive localized breast cancer: Updated results from the BERENICE study

Background Anti-HER2 therapies are associated with a risk of cardiac toxicity, particularly as part of anthracycline-based regimens. BERENICE (NCT02132949), a nonrandomized, Phase 2 cardiac safety study showed neoadjuvant treatment with pertuzumab (P) + trastuzumab (H) and 2 common anthracycline–taxane-based regimens had a safety profile consistent with prior studies of P+H, and was associated with high pathologic complete response rates. Here we report safety data from the P+H adjuvant treatment period (AP).

Methods Patients (pts) with centrally confirmed, localized HER2-positive breast cancer and normal cardiac function received 4 q2w dose-dense doxorubicin and cyclophosphamide cycles (60/600mg/m2) then 12 qw paclitaxel injections (80mg/m2; Cohort A), or 4 q3w fluorouracil/epirubicin/cyclophosphamide cycles (500/100/600 mg/m2) then 4 q3w docetaxel cycles (75mg/m2, up to 100mg/m2;Cohort B). In both cohorts, 4 q3w cycles of P (loading:840mg; maintenance:420mg) + H (loading:8mg/kg; maintenance:6mg/kg) were started with taxane therapy and continued in the adjuvant setting (for up to 13 cycles to complete 1 year of treatment). Surgery was scheduled after 8 cycles of preoperative therapy. Primary endpoints were incidence of New York Heart Association (NYHA) Class III/IV heart failure and incidence of left ventricular ejection fraction (LVEF) declines (≥10%-points from baseline to <50%; asymptomatic and symptomatic events) assessed by ECHO/MUGA. Confirmed LVEF declines were defined as significant LVEF declines at 2 consecutive visits.

Results In total, 397 pts received ≥1 dose of study medication and were included in the overall treatment period (OTP) safety analysis. Of these, 371 (Cohort A:181; Cohort B:190) pts entered the AP and were included in the AP safety analysis. Mean (SD) number of AP treatment cycles of P and H were 12.3 (2.0) in Cohort A and 12.3 (2.2) in Cohort B. In the AP, incidence of heart failure was minimal (0.5%) and confirmed LVEF decline incidence was low (Table 1).

Table 1: Cardiac AE Cohort ACohort B OTP n=199AP n=181OTP n=198OTP n=190NYHA Class III/IV heart failure    Events, n4011Pts with event, n (%)3(1.5)01(0.5)1(0.5)LVEF decline    Events, n36223429Pts with LVEF decline, n (%)21(10.6)14(7.7)22(11.1)20(10.5)Pts with confirmed LVEF decline, n (%)7(3.5)5(2.8)7(3.5)6(3.2)

General adverse events (AEs) are shown in Table 2; 26 (14.4%) pts in Cohort A and 45 (23.7%) in Cohort B had diarrhea AEs (mostly grade 1).

Table 2: General AE Cohort ACohort BPts, n (%)OTP n=199AP n=181OTP n=198AP n=190Any AE198(99.5)171(94.5)198(100.0)171(90.0)Grade ≥3 AE109(54.8)23(12.7)126(63.6)40(21.1)Serious AE54(27.1)15(8.3)61(30.8)17(8.9)AE leading to P or H discontinuation19(9.5)9(5.0)14(7.1)11(5.8)

Conclusion P+H in the adjuvant setting, following P+H with anthracycline-based regimens in the neoadjuvant setting, are associated with low incidence of cardiac AEs. Cardiac safety results for P+H in the AP and OTP of BERENICE were consistent with results from prior studies evaluating adjuvant treatment with single-agent H, suggesting the addition of P to H in the adjuvant setting does not increase cardiac toxicity.

Citation Format: Dang C, Ewer MS, Delaloge S, Ferrero J-M, Verrill M, Colomer R, Vieira C, de la Cruz Merino L, Lucas J, Werner TL, Douthwaite H, Bradley D, Waldron-Lynch M, Eng-Wong J, Swain SM. Safety of adjuvant treatment with pertuzumab plus trastuzumab after neoadjuvant anthracycline-based chemotherapy in patients with HER2-positive localized breast cancer: Updated results from the BERENICE study [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-20-04.

Abstract OT1-02-10: A phase 2 study of poziotinib in patients with HER2-positive metastatic breast cancer (MBC) who have received prior HER2 regimens for MBC

Background: Poziotinib is a novel, oral, quinazoline-based pan-HER inhibitor that irreversibly blocks signaling through the epidermal growth factor receptor (EGFR) family of tyrosine-kinase receptors, including EGFR (HER1/ErbB1/EGFR), HER2 (ErbB2), and HER4 (ErbB4), as well as HER receptor mutations. This, in turn, leads to inhibition of the proliferation of tumor cells that overexpress these receptors. It is well established that breast cancers are associated with a mutation in, or overexpression of, members of the EGFR receptor family. The primary objective of this Phase 2 study is to evaluate the Objective Response Rate (ORR) of poziotinib in patients with human epidermal growth factor receptor 2 (HER2)-positive MBC. The secondary efficacy variables are Progression-Free Survival (PFS), Disease Control Rate (DCR), Overall Survival (OS), and Time to Progression (TTP).

Trial Design: This is a Phase 2, open-label, multicenter study to evaluate the efficacy, safety and tolerability of poziotinib in patients with HER2-positive MBC who have received at least 2 prior HER2- directed treatment regimens. Each treatment cycle is 21 days in duration. During each cycle, eligible patients receive 24 mg of poziotinib orally (as three 8-mg tablets) once daily for 14 days, followed by a 7 day treatment-free period.

Eligibility Criteria: Eligible patients are at least 18 years of age, have confirmed HER2 overexpression, adequate hematologic, renal and hepatic function, and have received at least 2 prior HER2-directed therapy regimens, including trastuzumab and trastuzumab emtansine (TDM-1). Patients are excluded if they have prior exposure to poziotinib, a history of congestive heart failure, left ventricular ejection fraction <50%, unable to take oral medications, or have conditions that cause malabsorption. A 30 day wash out period from previous chemotherapeutic or radiation therapies is required.

Statistical Methods: The purpose of this study is to evaluate the efficacy of poziotinib compared to the efficacy of other standard HER2-positive breast cancer treatments as reported in the literature. The ORR will be analyzed descriptively along with the 95% CI. The secondary efficacy variables will be analyzed descriptively.

Target Accrual: Approximately 70 patients. Enrollment began February 2016.

Contact Information: For more information or to refer a patient,

email: spi-poz-201@sppirx.com or fax: 1-949-398-9711.

Citation Format: Lathrop K, Lucas J, Vacirca JL, Bhat G, Choi MR, Naughton M. A phase 2 study of poziotinib in patients with HER2-positive metastatic breast cancer (MBC) who have received prior HER2 regimens for MBC [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr OT1-02-10.