Mika K. Derynck

Clinical Activity of Pertuzumab (rhuMAb 2C4), a HER Dimerization Inhibitor, in Advanced Ovarian Cancer: Potential Predictive Relationship With Tumor HER2 Activation Status

PURPOSE Ovarian cancers (OCs) frequently have HER2 activation in the absence of HER2 overexpression. Pertuzumab, a humanized antibody that prevents HER2 dimerization and inhibits multiple HER-mediated pathways, was studied in a phase II, multicenter trial in advanced, refractory OC. PATIENTS AND METHODS Sixty-one patients (cohort 1) with relapsed OC received a loading dose of 840 mg pertuzumab intravenously followed by 420 mg every 3 weeks; 62 patients (cohort 2) received 1,050 mg every 3 weeks. Response rate was the primary end point. Fresh tumor biopsies were obtained in cohort 1 to assay for phosphorylated HER2 (pHER2). RESULTS Median age was 57 years and median number of prior chemotherapy regimens was five. Fifty-five patients in cohort 1 and 62 patients in cohort 2 were assessable for efficacy. There were five partial responses (response rate [RR] = 4.3%; 95% CI, 1.7% to 9.4%), eight patients (6.8%) with stable disease (SD) lasting at least 6 months, and 10 patients with CA-125 reduction of at least 50% (includes two partial responses and four patients with SD > or = 6 months; total clinical activity, 14.5%). Median progression-free survival (PFS) was 6.6 weeks. Eight of 28 tumor biopsies (28.6%) were pHER2+ by enzyme-linked immunosorbent assay (ELISA; without gene amplification). Median PFS for pHER2+ patients was 20.9 weeks (n = 8) versus 5.8 weeks for pHER2- (n = 20; P = .14) and 9.1 weeks for unknown pHER2 status (n = 27). Pertuzumab was well tolerated with diarrhea in 69.1% (11.4% grade 3, no grade 4). Five patients had asymptomatic left ventricular ejection fraction decreases to less than 50% (one confirmed by central facility). CONCLUSION Pertuzumab is well tolerated with a RR of 4.3% in heavily-pretreated OC patients. Further studies on pHER2 as a diagnostic are warranted.

Target-specific utilization of transcriptional regulatory surfaces by the glucocorticoid receptor

The glucocorticoid receptor (GR) activates or represses transcription depending on the sequence and architecture of the glucocorticoid response elements in target genes and the availability and activity of interacting cofactors. Numerous GR cofactors have been identified, but they alone are insufficient to dictate the specificity of GR action. Furthermore, the role of different functional surfaces on the receptor itself in regulating its targets is unclear, due in part to the paucity of known target genes. Using DNA microarrays and real-time quantitative PCR, we identified genes transcriptionally activated by GR, in a translation-independent manner, in two human cell lines. We then assessed in U2OS osteosarcoma cells the consequences of individually disrupting three GR domains, the N-terminal activation function (AF) 1, the C-terminal AF2, or the dimer interface, on activation of these genes. We found that GR targets differed in their requirements for AF1 or AF2, and that the dimer interface was dispensable for activation of some genes in each class. Thus, in a single cell type, different GR surfaces were used in a gene-specific manner. These findings have strong implications for the nature of gene response element signaling, the composition and structure of regulatory complexes, and the mechanisms of context-specific transcriptional regulation.

Prospective, Multicenter, Randomized Phase II Trial of the Herbal Supplement, PC-SPES, and Diethylstilbestrol in Patients With Androgen-Independent Prostate Cancer

PURPOSE To evaluate the herbal combination, PC-SPES, and diethylstilbestrol (DES) in patients with androgen independent prostate cancer (AIPC). PATIENTS AND METHODS A randomized phase II study was conducted with cross-over design. Patients were randomly assigned to receive either three PC-SPES capsules orally three times a day or DES 3 mg orally once a day. Prophylactic warfarin was administered. At clinical or prostate-specific antigen progression, patients received the other therapy. The study closed prematurely after PC-SPES was withdrawn from the market. Chemical analyses were performed on multiple lots of PC-SPES. RESULTS Ninety patients were enrolled, of whom 85 were assessable for response. Prostate-specific antigen declines > or = 50% were noted in 40% (95% CI, 25% to 56%) with PC-SPES, and 24% (95% CI, 12% to 39%) with DES. Median response duration was not reached with PC-SPES, and was 3.8 months with DES. Median time to progression for randomly assigned patients was 5.5 months for PC-SPES and 2.9 months for DES. Common toxicities included mild fatigue, gynecomastia, and mastodynia. Five thromboembolic events occurred (one PC-SPES, four DES). Responses in the cross-over phase were inconclusive. Four lots of PC-SPES had measurable quantities of DES, ranging from 0.01% to 3.1% of the dose used in the DES arm. Ethinyl estradiol was also detected in PC-SPES lots. CONCLUSION PC-SPES and DES demonstrate activity in AIPC and are well tolerated. However, the synthetic estrogens, DES and ethinyl estradiol, were detected in various lots of PC-SPES, including those used in this trial. Clinical trials that utilize herbal therapies must account for issues of purity and consistency.

Efficacy and Safety of Single-Agent Pertuzumab (rhuMAb 2C4), a Human Epidermal Growth Factor Receptor Dimerization Inhibitor, in Castration-Resistant Prostate Cancer After Progression From Taxane-Based Therapy

PURPOSE Pertuzumab represents a new class of targeted anticancer agents, human epidermal growth factor receptor (HER) dimerization inhibitors. The aim of this single-arm phase II clinical study was to assess the efficacy and safety of single-agent pertuzumab in castration-resistant prostate cancer (CRPC) patients who had experienced progression after prior chemotherapy. PATIENTS AND METHODS Patients received pertuzumab every 3 weeks. All castration-resistant patients had experienced progression after at least one taxane-based regimen. Patients received a loading dose of 840 mg pertuzumab (cycle 1) followed by 420 mg for subsequent cycles. The primary end point was overall response and safety. A separate retrospective analysis of actual survival time versus predicted survival time for a patient population with comparable prognostic features was performed. RESULTS Patients were enrolled (N = 42) and treated (n = 41). No patients had complete or partial response (as defined by Response Evaluation Criteria in Solid Tumors Group or 50% decline in prostate-specific antigen). Of 30 efficacy-assessable patients, five had stable disease (SD) for at least 23 weeks; one of five had SD for 36 weeks. Pertuzumab was well tolerated; diarrhea was the most common adverse effect (61.0%, grades 1 to 3). Retrospective analysis of survival using a validated nomogram suggested that survival was prolonged with pertuzumab treatment, compared with historic controls with similar baseline prognostic features. CONCLUSION Pertuzumab was well tolerated and resulted in no objective responses, but several patients had SD more than 23 weeks from a heavily pretreated population. Retrospective analysis suggested prolonged median survival time with pertuzumab compared with historical controls. Thus, inhibition of HER dimerization may have clinical utility in CRPC patients.

Activation of Stem-Cell Specific Genes by HOXA9 and HOXA10 Homeodomain Proteins in CD34+ Human Cord Blood Cells

There is growing evidence for a role of HOX homeodomain proteins in normal hematopoiesis. Several HOX genes, including HOXA9 and HOXA10, are expressed in primitive hematopoietic cells, implying a role in early hematopoietic differentiation. To identify potential target genes of these two closely related transcription factors, human CD34+ umbilical cord blood cells were transduced with vectors expressing either HOXA9 or HOXA10 and analyzed with cDNA micro‐arrays. Statistical analysis using significance analysis of microarrays revealed a common signature of several hundred genes, demonstrating that the transcriptomes of HOXA9 and HOXA10 largely overlap in this cellular context. Seven genes that were upregulated by both HOX proteins were validated by real‐time reverse transcription polymerase chain reaction. HOXA9 and HOXA10 showed positive regulation of genes in the Wnt pathway, including Wnt10B and two Wnt receptors Frizzled 1 and Frizzled 5, an important pathway for hematopoietic stem cell (HSC) self‐renewal. Other validated genes included v‐ets‐related gene (ERG), Iroquois 3 (IRX3), aldehyde dehydrogenase 1 (ALDH1), and very long–chain acyl‐CoA synthetase homolog 1 (VLCS‐H1). GenMAPP (Gene Micro Array Pathway Profiler) analysis indicated that HOXA10 repressed expression of several genes involved in heme biosynthesis and three globin genes, indicating a general suppression of erythroid differentiation. A number of genes regulated by HOXA9 and HOXA10 are expressed in normal HSC populations.