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Sym004 is an equimolar mixture of two monoclonal antibodies, futuximab and modotuximab, which non-competitively block the epidermal growth factor receptor (EGFR). Sym004 has been clinically tested for treatment of solid tumors. The present work characterizes the non-linear pharmacokinetics (PK) of Sym004 and its constituent antibodies and investigates two types of covariate models for interpreting the interindividual variability of Sym004 exposure. Sym004 serum concentration data from 330 cancer patients participating in four Phase 1 and 2 trials (n = 247 metastatic colorectal cancer, n = 87 various types advanced solid tumors) were pooled for non-linear mixed effects modeling. Dose regimens of 0.4-18 mg/kg Sym004 dosed by i.v. infusion weekly or every 2nd week were explored. The PK profiles for futuximab and modotuximab were parallel, and the parameter values for their population PK models were similar. The PK of Sym004 using the sum of the serum concentrations of futuximab and modotuximab was well captured by a 2-compartment model with parallel linear and saturable, Michaelis-Menten-type elimination. The full covariate model including all plausible covariates included in a single step showed no impact on Sym004 exposure of age, Asian race, renal and hepatic function, tumor type and previous anti-EGFR treatments. The reduced covariate model contained statistically and potentially clinically significant influences of body weight, albumin, sex and baseline tumor size. Population PK modeling and covariate analysis of Sym004 were feasible using the sum of the serum concentrations of the two constituent antibodies. Full and reduced covariate models provided insights into which covariates may be clinically relevant for dose modifications and thus may need further exploration.

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.

Purpose The purpose of the trial was to assess the efficacy and tolerability of Sym004, a novel 1:1 mixture of two chimeric monoclonal antibodies (992 and 1024) targeting non-overlapping epitopes of the anti-epidermal growth factor receptor (EGFR), in patients with squamous cell carcinoma of the head and neck (SCCHN). Methods Incurable, recurrent and/or metastatic SCCHN patients with acquired resistance to anti-EGFR monoclonal antibody-containing treatment received weekly infusions of 12 mg/kg Sym004 until disease progression or unacceptable toxicity. Results Among the 26 patients treated with Sym004, the proportion of patients alive without disease progression at 6 months was 12 % (95 % CI 139 %). The median duration of progression-free survival was 82 days (95 % CI 41140 days). Of 19 patients evaluable for response, eight showed a decrease in the sum of the largest diameter in their target lesions (median 11 %; range 727 %). The best overall response was stable disease in 13 patients (50 %). Paired biopsies showed a significant down-regulation of EGFR in both skin and tumors following exposure to Sym004. All patients had EGFR-related adverse events, including grade 3 skin toxicities and grade ≥3 hypomagnesemia reported in 13 (50 %) and 10 (38 %) of 26 patients, respectively. One event fulfilling the protocol-defined criteria for infusion-related reactions (grade 2) was reported. No anti-drug antibodies were detected. Conclusions The marked EGFR down-regulation shown in target tissues supports the proposed mechanism of action of Sym004. This trial revealed modest anti-tumor activity of Sym004 in extensively pretreated advanced SCCHN patients.

Purpose: Sym004 is a novel therapeutic antibody mixture product comprising two unmarketed monoclonal antibodies (mAb) targeting the epidermal growth factor receptor (EGFR). In previous preclinical proof-of-concept studies, Sym004 was shown to elicit superior cancer cell growth inhibition activities compared with marketed anti-EGFR mAbs. This article describes the design and results of the preclinical safety program conducted to support early clinical development of Sym004. Experimental Design: Tissue cryosections from various species were stained with Sym004 to evaluate tissue cross reactivity. The pharmacokinetics of Sym004 were evaluated in a mouse xenograft model and in Cynomolgus monkeys. Monkeys received once weekly intravenous infusions of Sym004 in the range 2 to 24 mg/kg for 6 to 8 weeks. Cetuximab (a marketed anti-EGFR mAb) and the individual antibodies comprising Sym004 were included in the repeat-dose toxicity studies at single-dose level. Results: Sym004 had a staining pattern similar to cetuximab in tissue panels from both human and non-human primates. Once weekly dosing of Sym004 to Cynomolgus monkeys did not cause accumulation, whereas administration of the individual antibodies resulted in prolonged half-life and accumulation. In direct comparisons with cetuximab, Sym004 did not induce any distinct or novel adverse findings in the animals. However, an early onset of pronounced, reversible, and anticipated anti-EGFR–mediated pharmacologic effects, such as skin rash, dehydration, and liquid feces, was observed. Only minor adverse effects were recorded in animals treated with the individual antibodies comprising Sym004. Conclusion: Sym004 was well tolerated and did not induce any unexpected toxicities. The preclinical safety data enabled initiation of the ongoing clinical development. Clin Cancer Res; 17(18); 5962–72. ©2011 AACR.

496 Background: Sym004 consists of two anti-EGFR monoclonal antibodies (futuximab and modotuximab) directed against non-overlapping epitopes in the EGFR domain III. Sym004 induces rapid and efficient removal of the EGFR from the cancer cell surface by triggering EGFR internalization and degradation and has shown promising efficacy in mCRC patients. Based upon a post-hoc analysis of a Phase 2 study, a Phase 3 trial in genomically selected mCRC patients is in preparation. Methods: The aim was to establish a popPK model for Sym004 in order to i) evaluate impact of covariates (intrinsic and extrinsic factors) on Sym004 exposure and ii) provide exposure metrics for a PK/PD analysis. Sym004 serum concentrations were obtained from 330 patients with mCRC (n = 247) or advanced solid tumors (studies Sym004-01, Sym004-02, Sym004-05 and Sym004-06). Sym004 (0.4-18 mg/kg) was dosed by i.v. infusion weekly or every 2nd week, or as a 9 mg/kg loading dose followed by 6 mg/kg weekly (9/6 mg/kg weekly). Non-linear mixed effects modelling was done in NONMEM v7.3.0. Covariates evaluated included body weight, age, sex, race, albumin, renal function, hepatic function, tumor type and size, ECOG and previous anti-EGFR treatments. Results: The base popPK model was a 2-compartment model with linear and non-linear Michaelis-Menten-type elimination and a priori inclusion of body weight on CL, Vmax, V1 and V2. The model captured the non-linear PK well. The final covariate model retained covariates whose point estimates were outside the range of 0.8 to 1.25 and whose 90% confidence intervals did not overlap with the null value and included only body weight and albumin. Inter-individual variability was estimated for CL, Vmax and V1 and was in the range of 18-30%. Simulations were used to assess the clinical relevance of the covariates as judged by the magnitude of the change in exposure of the Phase 3 dose regimen of 9/6 mg/kg weekly. Conclusions: The popPK model described the Sym004 PK data well. No covariates were present that changed the Sym004 exposure in a clinically significant manner which would necessitate a dose modification. The model is suitable for simulating the Sym004 PK for PK/PD analyses. Clinical trial information: NCT01117428,NCT01417936,NCT02083653,NCT01955473.

Tumor growth in the context of EGFR inhibitor resistance may remain EGFR-dependent and is mediated by mechanisms including compensatory ligand upregulation and de novo gene alterations. Sym004 is a two-antibody mixture targeting nonoverlapping EGFR epitopes. In preclinical models, Sym004 causes significant EGFR internalization and degradation, which translates into superior growth inhibition in the presence of ligands. In this phase I trial, we observed grade 3 skin toxicity and hypomagnesemia as mechanism-based dose-limiting events during dose escalation. In dose-expansion cohorts of 9 and 12 mg/kg of Sym004 weekly, patients with metastatic colorectal cancer and acquired EGFR inhibitor resistance were enrolled; 17 of 39 patients (44%) had tumor shrinkage, with 5 patients (13%) achieving partial response. Pharmacodynamic studies confirmed marked Sym004-induced EGFR downmodulation. MET gene amplification emerged in 1 patient during Sym004 treatment, and a partial response was seen in a patient with EGFRS492R mutation that is predictive of cetuximab resistance. Significance: Potent EGFR downmodulation with Sym004 in patients with metastatic colorectal cancer and acquired resistance to cetuximab/panitumumab translates into significant antitumor activity and validates the preclinical hypothesis that a proportion of tumors remains dependent on EGFR signaling. Further clinical development and expanded correlative analyses of response patterns with secondary RAS/EGFR mutations are warranted. Cancer Discov; 5(6);598–609. ©2015 AACR. See related commentary by Stintzing and Heinemann, p. 578 This article is highlighted in the In This Issue feature, p. 565

Rozrolimupab, a recombinant mixture of 25 fully human RhD-specific monoclonal antibodies, represents a new class of recombinant human antibody mixtures. In a phase 1 or 2 dose escalation study, RhD+ patients (61 subjects) with primary immune thrombocytopenia received a single intravenous dose of rozrolimupab ranging from 75 to 300 μg/kg. The primary outcome was the occurrence of adverse events. The principal secondary outcome was the effect on platelet levels 7 days after the treatment. The most common adverse events were headache and pyrexia, mostly mild, and reported in 20% and 13% of the patients, respectively, without dose relationship. Rozrolimupab caused an expected transient reduction of hemoglobin concentration in the majority of the patients. At the dose of 300 μg/kg platelet responses, defined as platelet count ≥ 30 × 109/L and an increase in platelet count by > 20 × 109/L from baseline were observed after 72 hours and persisted for at least 7 days in 8 of 13 patients (62%). Platelet responses were observed within 24 hours in 23% of patients and lasted for a median of 14 days. Rozrolimupab was well tolerated and elicited rapid platelet responses in patients with immune thrombocytopenia and may be a useful alternative to plasma-derived products. This trial is registered at www.clinicaltrials.gov as #NCT00718692.

3551 Background: Preclinical models suggest that WT KRAS mCRC may retain EGFR dependency despite resistance developed to anti-EGFR mAb treatment (eg, cetuximab or panitumumab). Sym004 is the first-...

3551 Background: KRAS wt mCRC pts progressing on chemotherapy and anti-EGFR mAbs have limited treatment options. Sym004 is a first-in-class drug mixture of two mAbs targeting non-overlapping epitopes on the EGFR, causing its internalization and degradation. With this unique mechanism of action, Sym004 overcomes acquired resistance to anti-EGFR mAbs in preclinical studies. Methods: Open-label, multicenter trial assessing safety (primary endpoint) and efficacy of 2 dose levels of Sym004 in KRAS wt mCRC pts with prior clinical benefit to anti-EGFR mAbs and subsequent progression during or within 6 months after treatment cessation. Sym004 was administered until disease progression or unacceptable toxicity. Tumor responses were evaluated centrally according to RECIST criteria. Paired skin and tumor biopsies were obtained at baseline and week 4. Results: In total, 42 pts were enrolled at 9 mg/kg (13) and 12 mg/kg (29). Median age was 66 years and median number of prior treatment lines 3. Central radiology review was performed in 12/13 (92%) pts at 9 mg/kg and 27/29 (93%) pts at 12 mg/kg. Tumor shrinkage > 10% was documented in 4/12 (33%) pts at 9 mg/kg, with partial response (PR) in 1/12 (8%) and stable disease (SD) in 9/12 (75%). At 12 mg/kg, 7/27 (26%) pts had > 10% tumor shrinkage, with PR in 3/27 (11%) and SD in 15/27 (56%). Median progression-free survival was 13.6 weeks (95% CI: 5.3-23) and 13.7 weeks (95% CI: 5.9-18.6), respectively. Duration of response for pts with PR was 5.6-17.6 weeks. Grade 3 or higher toxicity included skin rash in 26/42 (62%), hypomagnesemia in 16/42 (38%) and diarrhea in 2/42 (8%). Adverse events were manageable with dose reduction and supportive medication. There were no indications of immunogenicity. Pharmacodynamic analysis in serial tumor samples showed profound down-regulation of EGFR and reduction in proliferation marker Ki67. Conclusions: Sym004 at weekly doses of 9 and 12 mg/kg showed significant clinical activity in anti-EGFR treatment-refractory KRAS wt mCRC pts, clearly demonstrating proof-of-concept. Serial biopsies confirmed its mechanism of action. No unexpected adverse events were observed. Clinical trial information: NCT01117428.

6002 Background: Sym004 is a first-in-class drug mixture of two mAbs targeting non-overlapping epitopes on the EGFR. In preclinical models, Sym004 exhibited more pronounced EGFR internalization, degradation and tumor growth inhibition than cetuximab. Sym004 was investigated as monotherapy in palliative squamous cell carcinoma of the head and neck (SCCHN) patients (pts). Methods: SCCHN pts progressing after anti-EGFR mAbs for palliation were eligible. Documented clinical benefit (PR, CR or SD for at least 8 weeks according to RECIST) on an anti-EGFR mAb-containing regimen followed by disease progression during or within 12 weeks after treatment cessation was required. The primary endpoint of this multicentre single arm trial was centrally evaluated progression-free survival (PFS), estimated by median PFS and 24 week progression free rate. Secondary endpoints included objective tumor response, safety, biomarkers and pharmacokinetics. Pts received weekly iv infusions of 12 mg/kg Sym004 until disease progression. Tumor evaluation was performed week 6, 12 and every 8 weeks thereafter. Results: Based on the statistical hypothesis, 26 pts were included, of whom 23 had progressed while on anti-EGFR mAb treatment. One of 19 evaluable pts was HPV positive and no EGFRvIII mutation was detected in 21 evaluable pts. No anti-drug antibodies were detected. Independent central review of CT/MRI scans from 20 evaluable pts showed tumor shrinkage in 8 pts (% decrease in sum of the largest diameters: 6.5, 7.1, 9.6, 10.2, 11.3, 13.6, 16.7, 27.1) and 14 pts had SD as best overall response. Median PFS was 82 days (95% CI: 41, 140) and 24 week progression free rate was 12% (95% CI: 1, 39). During treatment 25/26 (96%) pts developed skin rash with ≥ grade 3 reported in 11/26 (42%) pts. Hypomagnesemia ≥ grade 3 was reported in 10/26 (38%) pts. Sym004 treatment resulted in a marked down regulation of EGFR in centrally reviewed biopsies from skin and tumors. Conclusions: Sym004 demonstrated clinical activity in heavily pretreated, predominately HPV negative pts with advanced SCCHN previously progressing on or after anti-EGFR mAbs. No unexpected toxicities were reported. Clinical trial information: NCT01417936.

3089 Background: Sym004 is a recombinant antibody 1:1 mixture of two chimeric anti-EGFR mAbs, which elicits superior cancer cell growth inhibition in preclinical models. Uniquely, Sym004 mediates cell surface receptor removal by triggering EGFR internalization and degradation. Results from a first-in-human multicenter trial evaluating safety and tolerability of multiple doses of Sym004 are reported. Methods: The trial comprises a dose-escalating part A (0.4 mg/kg-12 mg/kg) with classical 3+3 design after the first 2 cohorts and an extension part B at maximum tolerated dose (MTD). Patients (pts) received weekly IV infusions of Sym004 until disease progression or unacceptable toxicity. Pharmacokinetics and safety is evaluated weekly, with dose-limiting toxicities (DLT) assessed in the first 4 weeks, and tumor response every 8 weeks. Results: In part A, 17 pts (median age 60 years) were treated with doses up to 9 mg/kg without reaching the MTD: 0.4 mg/kg (1 had 6 doses), 0.75 mg/kg (1 had 35* doses), 1.5 mg/...

Epidermal growth factor receptor (EGFR) is a well validated oncology target for monoclonal antibodies (mAb's). Symphogen is developing a novel and more efficacious anti-EGFR therapy to treat cancer patients with EGFR-dependent tumors. Sym004 is a recombinant antibody product consisting of a 1:1 mixture of two chimeric IgG1 mAb's targeting non-overlapping epitopes of EGFR. Preclinical proof-of-concept studies have shown that the Sym004 mixture is superior to existing anti-EGFR mAb's currently in clinical use (1). The nonclinical safety data of Sym004 are presented. The studies were designed to evaluate toxicity and pharmacokinetics of Sym004 as well as the individual antibodies comprising Sym004. No apparent accumulation was observed upon weekly dosing of Sym004 to non-human primates for eight consecutive weeks, whereas, a prolonged half life and accumulation were noted for both of the individual antibodies if these were administered alone. Weekly administration of Sym004 to non-human primates was well tolerated although dose limiting toxicity was observed in a dose-range-finding toxicology study. In a head-to-head comparison with the licensed anti-EGFR mAb, cetuximab (Erbitux®), weekly administration of Sym004 did not induce any distinct or novel adverse findings in the animals. However, and in accordance with the enhanced pharmacological profile of Sym004, an accelerated onset of anticipated anti-EGFR-mediated effects (skin rash and liquid faeces) was observed compared to cetuximab. None or only minor effects were observed in the animals treated with the individual antibodies comprising Sym004. All experimental observations, except a single case of rash, showed reversibility during the 4-week treatment free recovery period. In tissue cross reactivity studies, Sym004 had a staining pattern similar to cetuximab in a full tissue panel from both human and non human primates. In conclusion, Sym004 is considered to be safe, and the nonclinical safety data supported the initiation of the currently ongoing Phase I/II trial. 1. Pedersen MW et al. Cancer Res; 70(2) January 15, 2010 Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1752. doi:10.1158/1538-7445.AM2011-1752