Description: Purpose: CD19, a B-cell lineage-specific marker, is highly represented in B-cell malignancies and an attractive target for therapeutic interventions. MGD011 is a CD19 x CD3 DART bispecific protein designed to redirect T lymphocytes to eliminate CD19-expressing cells. MGD011 has been engineered with a modified human Fc domain for improved pharmacokinetic (PK) properties and designed to cross-react with the corresponding antigens in cynomolgus monkeys. Here, we report on the preclinical activity, safety and PK properties of MGD011. Experimental Design: The activity of MGD011 was evaluated in several in vitro and in vivo models. PK, safety and pharmacodynamic activity was also assessed in dose-escalation and repeat-dose studies of MGD011 administered once weekly in cynomolgus monkeys. Results: MGD011 mediated killing of human B-cell lymphoma lines by human or cynomolgus monkey PBMCs as well as autologous B-cell depletion in PBMCs from both species. MGD011-mediated killing was accompanied by target-dependent T-cell activation and expansion, cytokine release and upregulation of perforin and granzyme B. MGD011 demonstrated antitumor activity against localized and disseminated lymphoma xenografts reconstituted with human PBMCs. In cynomolgus monkeys, MGD011 displayed a terminal half-life of 6.7 days; once weekly intravenous infusion of MGD011 at doses up to 100 μg/kg, the highest dose tested, was well tolerated and resulted in dose-dependent, durable decreases in circulating B cells accompanied by profound reductions of B lymphocytes in lymphoid organs. Conclusions: The preclinical activity, safety and PK profile support clinical investigation of MGD011 as a therapeutic candidate for the treatment of B-cell malignancies. Clin Cancer Res; 23(6); 1506–18. ©2016 AACR .

Description: Breast cancer research is hampered by difficulties in obtaining and studying primary human breast tissue, and by the lack of in vivo preclinical models that reflect patient tumor biology accurately. To overcome these limitations, we propagated a cohort of human breast tumors grown in the epithelium-free mammary fat pad of severe combined immunodeficient (SCID)/Beige and nonobese diabetic (NOD)/SCID/IL-2γ-receptor null (NSG) mice under a series of transplant conditions. Both models yielded stably transplantable xenografts at comparably high rates (∼21% and ∼19%, respectively). Of the conditions tested, xenograft take rate was highest in the presence of a low-dose estradiol pellet. Overall, 32 stably transplantable xenograft lines were established, representing 25 unique patients. Most tumors yielding xenografts were “triple-negative” [estrogen receptor (ER)−progesterone receptor (PR)−HER2+; n = 19]. However, we established lines from 3 ER−PR−HER2+ tumors, one ER+PR−HER2−, one ER+PR+HER2−, and one “triple-positive” (ER+PR+HER2+) tumor. Serially passaged xenografts show biologic consistency with the tumor of origin, are phenotypically stable across multiple transplant generations at the histologic, transcriptomic, proteomic, and genomic levels, and show comparable treatment responses as those observed clinically. Xenografts representing 12 patients, including 2 ER+ lines, showed metastasis to the mouse lung. These models thus serve as a renewable, quality-controlled tissue resource for preclinical studies investigating treatment response and metastasis. Cancer Res; 73(15); 4885–97. ©2013 AACR.

Description: Purpose: We investigated the efficacy and underlying molecular mechanism of a novel chemopreventive strategy combining EGF receptor (EGFR) tyrosine kinase inhibitor (TKI) with cyclooxygenase-2 inhibitor (COX-2I). Experimental Design: We examined the inhibition of tumor cell growth by combined EGFR-TKI (erlotinib) and COX-2I (celecoxib) treatment using head and neck cancer cell lines and a preventive xenograft model. We studied the antiangiogenic activity of these agents and examined the affected signaling pathways by immunoblotting analysis in tumor cell lysates and immunohistochemistry (IHC) and enzyme immunoassay (EIA) analyses on the mouse xenograft tissues and blood, respectively. Biomarkers in these signaling pathways were studied by IHC, EIA, and an antibody array analysis in samples collected from participants in a phase I chemoprevention trial of erlotinib and celecoxib. Results: The combined treatment inhibited head and neck cancer cell growth significantly more potently than either single agent alone in cell line and xenograft models, and resulted in greater inhibition of cell-cycle progression at G 1 phase than either single drug. The combined treatment modulated the EGFR and mTOR signaling pathways. A phase I chemoprevention trial of combined erlotinib and celecoxib revealed an overall pathologic response rate of 71% at time of data analysis. Analysis of tissue samples from participants consistently showed downregulation of EGFR, pERK, and pS6 levels after treatment, which correlated with clinical response. Conclusion: Treatment with erlotinib combined with celecoxib offers an effective chemopreventive approach through inhibition of EGFR and mTOR pathways, which may serve as potential biomarkers to monitor the intervention of this combination in the clinic. Clin Cancer Res; 19(5); 1244–56. ©2013 AACR .

Description: Purpose: Accumulating evidence supports the existence of breast cancer stem cells (BCSC), which are characterized by their capacity to self-renew and divide indefinitely and resistance to conventional therapies. The Notch pathway is important for stem cell renewal and is a potential target for BCSC-directed therapy. Experimental Design: Using human breast tumorgraft studies, we evaluated the impact of gamma secretase inhibitors (GSI) on the BCSC population and the efficacy of combining GSI with docetaxel treatment. The mouse experimental therapy paralleled a concurrent clinical trial in patients with advanced breast cancer, designed to determine the maximum-tolerated dose of the GSI, MK-0752, administered sequentially with docetaxel, and to evaluate BCSC markers in serial tumor biopsies. Results: Treatment with GSI reduced BCSCs in MC1 and BCM-2147 tumorgrafts by inhibition of the Notch pathway. GSI enhanced the efficacy of docetaxel in preclinical studies. In the clinical trial, 30 patients with advanced breast cancer were treated with escalating doses of MK-0752 plus docetaxel. Clinically, meaningful doses of both drugs were possible with manageable toxicity and preliminary evidence of efficacy. A decrease in CD44 + /CD24 – , ALDH + , and mammosphere-forming efficiency were observed in tumors of patients undergoing serial biopsies. Conclusions: These preclinical data show that pharmacologic inhibition of the Notch pathway can reduce BCSCs in breast tumorgraft models. The clinical trial shows feasibility of combination GSI and chemotherapy, and together these results encourage further study of Notch pathway inhibitors in combination with chemotherapy in breast cancer. Clin Cancer Res; 19(6); 1512–24. ©2012 AACR .

Description: Purpose: Two germline Fc- receptor (FCGR) polymorphisms, rs1801274 [ FCGR2A;His(H)131Arg(R) ] and rs396991 [ FCGR3A;Phe(F)158Val(V) ] produce altered proteins through amino acid substitutions; both are reported to be associated with cetuximab-related outcomes. We performed a validation of these polymorphisms in NCIC CTG CO.17, a randomized trial of cetuximab monotherapy in refractory, metastatic colorectal cancer expressing EGFR. Experimental Design: DNA extracted from formalin-fixed paraffin-embedded tissue was genotyped. In addition to log-rank tests, Cox proportional hazard models assessed their relationships with overall (OS) and progression-free survival (PFS), adjusting for clinically important prognostic factors, along with a polymorphism–treatment arm interaction term. Results: Somatic KRAS status was wild-type for exon 2 in 153 (52%) of 293 patients, from whom tumor DNA was available. For FCGR2A H/H , a genotype–treatment interaction for KRAS wild-type patients was observed for OS ( P = 0.03). In KRAS wild-type patients carrying FCGR2A H/H , cetuximab (vs. no cetuximab) improved survival substantially, with adjusted HRs (aHR) of 0.36 (OS) and 0.19 (PFS) and absolute benefits of 5.5 months (OS; P = 0.003) and 3.7 months (PFS; P = 0.02). In contrast, patients carrying FCGR2A R alleles ( H/R or R/R ) had aHRs of only 0.78 (OS; 2.8-month benefit) and 0.53 (PFS; 1.6-month benefit). No relationships were found for rs396991 ( FCGR3A ). Conclusions: In the CO.17 trial, cetuximab worked best for patients with KRAS wild-type colorectal cancers carrying FCGR2A H/H genotypes. Significantly lower benefits were observed in patients carrying germline FCGR2A R alleles. Clin Cancer Res; 22(10); 2435–44. ©2016 AACR .

Description: Purpose: Preclinical studies suggest that SNPs in the Fc gamma receptor ( FCGR ) genes influence response to rituximab, but the clinical relevance of this is uncertain. Experimental Design: We prospectively obtained specimens for genotyping in the rituximab extended schedule or re-treatment trial (RESORT) study, in which 408 previously untreated, low tumor burden follicular lymphoma (FL) patients were treated with single agent rituximab. Patients received rituximab in 4 weekly doses and responders were randomized to rituximab re-treatment (RR) upon progression versus maintenance rituximab (MR). SNP genotyping was performed in 321 consenting patients. Results: Response rates to initial therapy and response duration were correlated with the FCGR3A SNP at position 158 (rs396991) and the FCGR2A SNP at position 131 (rs1801274). The response rate to initial rituximab was 71%. No FCGR genotypes or grouping of genotypes were predictive of initial response. A total of 289 patients were randomized to RR ( n = 143) or to MR ( n = 146). With a median follow-up of 5.5 years, the 3-year response duration in the RR arm and the MR arm was 50% and 78%, respectively. Genotyping was available in 235 of 289 randomized patients. In patients receiving RR ( n = 115) or MR ( n = 120), response duration was not associated with any FCGR genotypes or genotype combinations. Conclusions: Based on this analysis of treatment-naïve, low tumor burden FL, we conclude that the FCGR3A and FCGR2A SNPs do not confer differential responsiveness to rituximab. Clin Cancer Res; 22(4); 821–6. ©2015 AACR . See related commentary by Cartron et al., p. 787

Description: Estrogen has a central role in the genesis and progression of breast cancers whether they are positive or negative for the estrogen receptor (ER). While therapies that disrupt estrogen biosynthesis or ER activity can treat these diseases in postmenopausal women, in younger women where ovarian function remains intact, these anti-estrogen therapies are not as effective. Moreover, emerging clinical evidence suggests that estrogen may promote other cancers. Thus, circulating estrogens may participate in cancer pathogenesis in ways that are not yet understood. In this study, we show that estrogen can promote the outgrowth of murine xenograft tumors established from patient-derived ER-negative breast cancer cells by influencing the mobilization and recruitment of a proangiogenic population of bone marrow–derived myeloid cells. ERα expression was necessary and sufficient in the bone marrow–derived cells themselves to promote tumor formation in response to estrogen. Our findings reveal a novel way in which estrogen promotes tumor formation, with implications for the development and application of anti-estrogen therapies to treat cancer in premenopausal women. Cancer Res; 72(11); 2705–13. ©2012 AACR.