BACKGROUND In patients with metastatic breast cancer that is positive for human epidermal growth factor receptor 2 (HER2), progression-free survival was significantly improved after first-line therapy with pertuzumab, trastuzumab, and docetaxel, as compared with placebo, trastuzumab, and docetaxel. Overall survival was significantly improved with pertuzumab in an interim analysis without the median being reached. We report final prespecified overall survival results with a median follow-up of 50 months. METHODS We randomly assigned patients with metastatic breast cancer who had not received previous chemotherapy or anti-HER2 therapy for their metastatic disease to receive the pertuzumab combination or the placebo combination. The secondary end points of overall survival, investigator-assessed progression-free survival, independently assessed duration of response, and safety are reported. Sensitivity analyses were adjusted for patients who crossed over from placebo to pertuzumab after the interim analysis. RESULTS The median overall survival was 56.5 months (95% confidence interval [CI], 49.3 to not reached) in the group receiving the pertuzumab combination, as compared with 40.8 months (95% CI, 35.8 to 48.3) in the group receiving the placebo combination (hazard ratio favoring the pertuzumab group, 0.68; 95% CI, 0.56 to 0.84; P<0.001), a difference of 15.7 months. This analysis was not adjusted for crossover to the pertuzumab group and is therefore conservative. Results of sensitivity analyses after adjustment for crossover were consistent. Median progression-free survival as assessed by investigators improved by 6.3 months in the pertuzumab group (hazard ratio, 0.68; 95% CI, 0.58 to 0.80). Pertuzumab extended the median duration of response by 7.7 months, as independently assessed. Most adverse events occurred during the administration of docetaxel in the two groups, with long-term cardiac safety maintained. CONCLUSIONS In patients with HER2-positive metastatic breast cancer, the addition of per tuzumab to trastuzumab and docetaxel, as compared with the addition of placebo, significantly improved the median overall survival to 56.5 months and extended the results of previous analyses showing the efficacy of this drug combination. (Funded by F. Hoffmann–La Roche and Genentech; CLEOPATRA ClinicalTrials.gov number, NCT00567190.)

Imprinted genes are expressed from only one of the parental alleles and are marked epigenetically by DNA methylation and histone modifications. The paternally expressed gene insulin-like growth-factor 2 (Igf2) is separated by approximately 100 kb from the maternally expressed noncoding gene H19 on mouse distal chromosome 7. Differentially methylated regions in Igf2 and H19 contain chromatin boundaries, silencers and activators and regulate the reciprocal expression of the two genes in a methylation-sensitive manner by allowing them exclusive access to a shared set of enhancers. Various chromatin models have been proposed that separate Igf2 and H19 into active and silent domains. Here we used a GAL4 knock-in approach as well as the chromosome conformation capture technique to show that the differentially methylated regions in the imprinted genes Igf2 and H19 interact in mice. These interactions are epigenetically regulated and partition maternal and paternal chromatin into distinct loops. This generates a simple epigenetic switch for Igf2 through which it moves between an active and a silent chromatin domain.

DNA methylation is usually associated with transcriptional silencing, but in the imprinted mouse Igf2 gene, the paternally expressed copy is methylated in two discrete differentially methylated regions (DMRs). DMR1 is located upstream of the fetal promoters and has been shown to be a methylation sensitive silencer. Here we examine the role of the intragenic DMR2 by gene targeting. In contrast to DMR1, deletion of DMR2 on the maternal allele did not lead to activation of the silent Igf2 gene. Deletion of a 54 bp methylated core region in DMR2 on the paternal allele, however, reduced Igf2 mRNA levels and was associated with fetal growth retardation. Nuclear run-on assays showed that the core region influenced transcription initiation, and luciferase reporter assays suggested that its methylation increases transcription. These results reveal a novel mechanism of gene expression whereby intragenic methylation can increase levels of transcription.

Purpose To assess the efficacy and safety of trastuzumab plus capecitabine with or without pertuzumab in patients with human epidermal growth factor receptor 2-positive metastatic breast cancer who experienced disease progression during or after trastuzumab-based therapy and received a prior taxane. Patients and Methods Patients were randomly assigned to arm A: trastuzumab 8 mg/kg → 6 mg/kg once every 3 weeks plus capecitabine 1,250 mg/m twice a day (2 weeks on, 1 week off, every 3 weeks); or arm B: pertuzumab 840 mg → 420 mg once every 3 weeks plus trastuzumab at the same dose and schedule as arm A plus capecitabine 1,000 mg/m on the same schedule as arm A. The primary end point was independent review facility-assessed progression-free survival (IRF PFS). Secondary end points included overall survival (OS) and safety. Hierarchical testing procedures were used to control type I error for statistical testing of IRF PFS, OS, and objective response rate. Results Randomly assigned (intent-to-treat) populations were 224 and 228 patients in arms A and B, respectively. Median IRF PFS at 28.6 and 25.3 months' median follow-up was 9.0 v 11.1 months (hazard ratio, 0.82; 95% CI, 0.65 to 1.02; P = .0731) and interim OS was 28.1 v 36.1 months (hazard ratio, 0.68; 95% CI, 0.51 to 0.90). The most common adverse events (all grades; incidence of ≥ 10% in either arm and ≥ 5% difference between arms) were hand-foot syndrome, nausea, and neutropenia in arm A, and diarrhea, rash, and nasopharyngitis in arm B. Conclusion The addition of pertuzumab to trastuzumab and capecitabine did not significantly improve IRF PFS. An 8-month increase in median OS to 36.1 months with pertuzumab was observed. Statistical significance for OS cannot be claimed because of the hierarchical testing of OS after the primary PFS end point; however, the magnitude of OS difference is in keeping with prior experience of pertuzumab in metastatic breast cancer. No new safety signals were identified.