Real-world effectiveness of post-trastuzumab emtansine treatment in patients with HER2-positive, unresectable and/or metastatic breast cancer: a retrospective observational study (KBCSG-TR 1917).

BACKGROUND: Trastuzumab emtansine (T-DM1) is a second-line standard therapy for patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer. Evidence regarding post-T-DM1 treatments is currently lacking. We evaluated the effectiveness of post-T-DM1 drug therapy in patients with HER2-positive, unresectable and/or metastatic breast cancer. METHODS: In this multicenter, retrospective, observational study, real-world clinical data of female patients with HER2-positive breast cancer who had a history of T-DM1 treatment were consecutively collected from five sites in Japan. We investigated the effectiveness of post-T-DM1 therapy by evaluating the real-world progression-free survival (rwPFS), time to treatment failure (TTF), overall survival (OS), objective response rate (ORR), and clinical benefit rate (CBR). Tumor response was assessed by investigators according to Response Evaluation Criteria in Solid Tumors (RECIST version 1.1) guidelines. Subgroup and exploratory analyses according to background factors were also undertaken. RESULTS: Of the 205 patients who received T-DM1 treatment between 1 January 2014 and 31 December 2018, 128 were included in this study. Among the 128 patients analyzed, 105 (82%) patients received anti-HER2 therapy and 23 (18%) patients received regimens without anti-HER2 therapy. Median (95% confidence interval [CI]) rwPFS, TTF, and OS were 5.7 (4.8-6.9) months, 5.6 (4.6-6.4) months, and 22.8 (18.2-32.4) months, respectively. CBR and ORR (95% CI) were 48% (38.8-56.7) and 23% (15.1-31.4), respectively. Cox-regression analysis showed that an ECOG PS score of 0, a HER2 immunohistochemistry score of 3+, recurrent type, ≥12 month duration of T-DM1 therapy, and anti-HER2 therapy were independent variables for rwPFS. An exploratory subgroup analysis of regimens after T-DM1 showed that those with anti-HER2 therapy had a median rwPFS of 6.3 and those without anti-HER2 therapy had a median rwPFS of 4.8 months. CONCLUSIONS: In the real-world setting in Japan, several post-T-DM1 regimens for patients with unresectable and/or metastatic HER2-positive breast cancer, including continuation of anti-HER2 therapy, showed some effectiveness; however, this effectiveness was insufficient. Novel therapeutic options are still needed for further improvement of PFS and OS in later treatment settings. TRIAL REGISTRATION: UMIN000038296 ; registered on 15 October 2019.

RUVBL1/RUVBL2 ATPase Activity Drives PAQosome Maturation, DNA Replication and Radioresistance in Lung Cancer.

RUVBL1 and RUVBL2 (collectively RUVBL1/2) are essential AAA+ ATPases that function as co-chaperones and have been implicated in cancer. Here we investigated the molecular and phenotypic role of RUVBL1/2 ATPase activity in non-small cell lung cancer (NSCLC). We find that RUVBL1/2 are overexpressed in NSCLC patient tumors, with high expression associated with poor survival. Utilizing a specific inhibitor of RUVBL1/2 ATPase activity, we show that RUVBL1/2 ATPase activity is necessary for the maturation or dissociation of the PAQosome, a large RUVBL1/2-dependent multiprotein complex. We also show that RUVBL1/2 have roles in DNA replication, as inhibition of its ATPase activity can cause S-phase arrest, which culminates in cancer cell death via replication catastrophe. While in vivo pharmacological inhibition of RUVBL1/2 results in modest antitumor activity, it synergizes with radiation in NSCLC, but not normal cells, an attractive property for future preclinical development.

Development of DS-5573a: A novel afucosylated mAb directed at B7-H3 with potent antitumor activity.

B7-H3 is highly overexpressed in a variety of human clinical tumors, and its expression is significantly associated with poor outcomes. In our study, we aimed to develop new antitumor mAbs by employing cancer cell immunization, and succeeded in generating a mouse anti-human B7-H3 antibody (M30) that shows antitumor activity. M30 was humanized (Hu-M30), and an afucosylated Hu-M30 (DS-5573a) was also generated. To assess the potency of DS-5573a as a therapeutic mAb, we characterized this mAb and evaluated its antitumor activity in vitro and in vivo. Flow cytometry analysis showed that B7-H3 proteins were expressed on various types of cancer cell lines broadly, and DS-5573a binds to IgC1 and IgC2 domains of human B7-H3. Antibody-dependent cellular cytotoxicity activity of DS-5573a was drastically enhanced against medium to high B7-H3-expressing cancer cell lines MDA-MB-231 and NCI-H322. DS-5573a also induced high antibody-dependent cellular cytotoxicity activity against low B7-H3-expressing cancer cell line COLO205, whereas Hu-M30 induced little activity against it. In addition, DS-5573a was found to be a novel anti-B7-H3 antibody which showed antibody-dependent cellular phagocytosis activity. Furthermore, DS-5573a showed dose-dependent and significant antitumor efficacy (0.03-3 mg/kg) in MDA-MB-231-bearing SCID mice (which have functional natural killer cells and macrophages), but little antitumor efficacy in NOG mice (which lack natural killer cells and have reduced macrophage function). These results suggest that antitumor activity of DS-5573a is mediated by effector cells, and this mAb could be a promising antitumor therapy for patients with a wide range of B7-H3-expressing tumors.

Human Sir2-related protein SIRT1 associates with the bHLH repressors HES1 and HEY2 and is involved in HES1- and HEY2-mediated transcriptional repression.

The Hairy-related bHLH proteins function as transcriptional repressors in most cases and play important roles in diverse aspects of metazoan development. Recently, it was shown that the Drosophila bHLH repressor proteins, Hairy and Deadpan, bind to and function with the NAD(+)-dependent histone deacetylase, Sir2. Here we demonstrate that the human Sir2 homologue, SIRT1, also physically associates with the human bHLH repressor proteins, hHES1 and hHEY2, both in vitro and in vivo. Moreover, using the reporter assay, we show that both SIRT1-dependent and -independent deacetylase pathways are involved in the transcriptional repressions mediated by these bHLH repressors. These results indicate that the molecular association between bHLH proteins and Sir2-related proteins is conserved among metazoans, from Drosophila to human, and suggest that the Sir2-bHLH interaction also plays important roles in human cells.