Trine Lindsted

Efficacy of Sym004 in Patients With Metastatic Colorectal Cancer With Acquired Resistance to Anti-EGFR Therapy and Molecularly Selected by Circulating Tumor DNA Analyses: A Phase 2 Randomized Clinical Trial

Importance Acquired resistance to anti-EGFR therapy (epidermal growth factor receptor) is frequently due to RAS and EGFR extracellular domain (ECD) mutations in metastatic colorectal cancer (mCRC). Some anti-EGFR–refractory patients retain tumor EGFR dependency potentially targetable by agents such as Sym004, which is a mixture of 2 nonoverlapping monoclonal antibodies targeting EGFR. Objective To determine if continuous blockade of EGFR by Sym004 has survival benefit. Design, Setting, and Participants Multicenter, phase 2, randomized, clinical trial comparing 2 regimens of Sym004 with investigator’s choice from March 6, 2014, through October 15, 2015. Circulating tumor DNA (ctDNA) was analyzed for biomarker and tracking clonal dynamics during treatment. Participants had wild-type KRAS exon 2 mCRC refractory to standard chemotherapy and acquired resistance to anti-EGFR monoclonal antibodies. Interventions Participants were randomly assigned in a 1:1:1 ratio to Sym004, 12 mg/kg/wk (arm A), Sym004, 9 mg/kg loading dose followed by 6 mg/kg/wk (arm B), or investigator’s choice of treatment (arm C). Main Outcomes and Measures Overall survival (OS). Secondary end points included preplanned exploratory biomarker analysis in ctDNA. Results A total of 254 patients were randomized (intent-to-treat [ITT] population) (median age, 63 [range, 34-91] years; 63% male; n = 160). Median OS in the ITT population was 7.9 months (95% CI, 6.5-9.9 months), 10.3 months (95% CI, 9.0-12.9 months), and 9.6 months (95% CI, 8.3-12.2 months) for arms A, B, and C, respectively (hazard ratio [HR], 1.31; 95% CI, 0.92-1.87 for A vs C; and HR, 0.97; 95% CI, 0.68-1.40 for B vs C). The ctDNA revealed high intrapatient genomic heterogeneity following anti-EGFR therapy. Sym004 effectively targeted EGFR ECD-mutated cancer cells, and a decrease in EGFR ECD ctDNA occurred in Sym004-treated patients. However, this did not translate into clinical benefit in patients with EGFR ECD mutations, likely owing to co-occurring resistance mechanisms. A subgroup of patients was defined by ctDNA (RAS/BRAF/EGFR ECD-mutation negative) associated with improved OS in Sym004-treated patients in arm B compared with arm C (median OS, 12.8 and 7.3 months, respectively). Conclusions and Relevance Sym004 did not improve OS in an unselected population of patients with mCRC and acquired anti-EGFR resistance. A prospective clinical validation of Sym004 efficacy in a ctDNA molecularly defined subgroup of patients with refractory mCRC is warranted. Trial Registration clinicaltrialsregister.eu Identifier: 2013-003829-29

Cetuximab Resistance in Squamous Carcinomas of the Upper Aerodigestive Tract Is Driven by Receptor Tyrosine Kinase Plasticity: Potential for mAb Mixtures.

Squamous cell carcinomas (SCC) arising in upper parts of the aerodigestive tract are among the leading causes of death worldwide. EGFR has been found to play an essential role in driving the malignancy of SCC of the upper aerodigestive tract (SCCUAT), but, despite this, clinical results using a range of different EGFR-targeted agents have been disappointing. Cetuximab is currently the only EGFR-targeted agent approved by the FDA for treatment of SCCUAT. However, intrinsic and acquired cetuximab resistance is a major problem for effective therapy. Thus, a better understanding of the mechanisms responsible for cetuximab resistance is valuable for development of the next generation of antibody therapeutics. In order to better understand the underlying mechanisms of cetuximab resistance in SCCUAT, we established from cetuximab-sensitive models cell lines with acquired resistance to cetuximab by continuous selective pressure in vitro and in vivo. Our results show that resistant clones maintain partial dependency on EGFR and that receptor tyrosine kinase plasticity mediated by HER3 and IGF1R plays an essential role. A multitarget mAb mixture against EGFR, HER3, and IGF1R was able to overcome cetuximab resistance in vitro. To our surprise, these findings could be extended to include SCCUAT cell lines with intrinsic resistance to cetuximab, suggesting that the triad consisting of EGFR, HER3, and IGF1R plays a key role in SCCUAT. Our results thus provide a rationale for simultaneous targeting of EGFR, HER3, and IGF1R in SCCUAT. Mol Cancer Ther; 15(7); 1614–26. ©2016 AACR.

Sym015: A Highly Efficacious Antibody Mixture against MET-Amplified Tumors

Purpose: Activation of the receptor tyrosine kinase MET is associated with poor clinical outcome in certain cancers. To target MET more effectively, we developed an antagonistic antibody mixture, Sym015, consisting of two humanized mAbs directed against nonoverlapping epitopes of MET. Experimental Design/Results: We screened a large panel of well-annotated human cancer cell lines and identified a subset with highly elevated MET expression. In particular, cell lines of lung cancer and gastric cancer origin demonstrated high MET expression and activation, and Sym015 triggered degradation of MET and significantly inhibited growth of these cell lines. Next, we tested Sym015 in patient- and cell line–derived xenograft models with high MET expression and/or MET exon 14 skipping alterations, and in models harboring MET amplification as a mechanism of resistance to EGFR-targeting agents. Sym015 effectively inhibited tumor growth in all these models and was superior to an analogue of emibetuzumab, a monoclonal IgG4 antibody against MET currently in clinical development. Sym015 also induced antibody-dependent cellular cytotoxicity (ADCC) in vitro, suggesting that secondary effector functions contribute to the efficacy of Sym015. Retrospectively, all responsive, high MET-expressing models were scored as highly MET-amplified by in situ hybridization, pointing to MET amplification as a predictive biomarker for efficacy. Preclinical toxicology studies in monkeys showed that Sym015 was well tolerated, with a pharmacokinetic profile supporting administration of Sym015 every second or third week in humans. Conclusions: The preclinical efficacy and safety data provide a clear rationale for the ongoing clinical studies of Sym015 in patients with MET-amplified tumors. Clin Cancer Res; 23(19); 5923–35. ©2017 AACR.

Abstract 1219: Sym015, a novel antibody mixture targeting non-overlapping epitopes of MET, effectively inhibits growth of MET dependent tumors and overcomes resistance to a single monoclonal antibody

The tyrosine kinase receptor MET is involved in progression of a variety of human cancers and constitutes a promising therapeutic target. Particularly, subsets of tumors originating from lung or gastric tissues appear to be truly MET dependent. MET dependency is driven by alterations, such as MET-gene amplification, MET-exon 14 deletion, kinase activating mutations, or autocrine HGF production. Furthermore, MET-amplification has been reported as a key mechanism of de novo resistance to EGFR targeting agents in lung and colorectal cancers. Sym015, a novel antibody mixture comprising two monoclonal antibodies targeting non-overlapping epitopes on the SEMA domain of MET, was shown to effectively inhibit cell growth in vitro through effective MET degradation. In the present study, we screened a large panel of highly annotated human cancer cell lines for sensitivity to Sym015 in order to identify potential markers of response. Sym015 effectively inhibited growth of cell lines with MET-amplification, MET-exon 14 deletion, and autocrine HGF production, including MET-amplified cell lines with acquired resistance to EGFR targeting agents. To validate the in vitro findings, a range of cell line- and patient-derived xenograft models with MET amplification or Exon 14 deletion were tested for sensitivity to Sym015 and an analogue of the clinical stage anti-MET monoclonal antibody emibetuzumab (LY2875358). Sym015 effectively inhibited growth of tumors with autocrine HGF production, MET-amplification, and/or Exon 14 deletion, and had superior activity compared to the emibetuzumab analogue in many of the models. Importantly, tumors with a partial response to the emibetuzumab analogue were strongly inhibited by subsequent treatment with Sym015 in two MET-amplified models, one of which also harbors a MET-exon 14 deletion. In summary, our findings demonstrate a potent antitumor effect of Sym015 in MET-dependent models. The data thus strongly support initiation of clinical trials for patients with MET-amplification and Exon 14 deletions. Citation Format: Thomas T. Poulsen, Michael M. Grandal, Helle J. Jacobsen, Dorte S. Hansen, Trine Lindsted, Mikkel W. Pedersen, Ivan D. Horak, Michael Kragh, Johan Lantto. Sym015, a novel antibody mixture targeting non-overlapping epitopes of MET, effectively inhibits growth of MET dependent tumors and overcomes resistance to a single monoclonal antibody. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1219.