Cergutuzumab amunaleukin (CEA-IL2v), a CEA-targeted IL-2 variant-based immunocytokine for combination cancer immunotherapy: Overcoming limitations of aldesleukin and conventional IL-2-based immunocytokines.

We developed cergutuzumab amunaleukin (CEA-IL2v, RG7813), a novel monomeric CEA-targeted immunocytokine, that comprises a single IL-2 variant (IL2v) moiety with abolished CD25 binding, fused to the C-terminus of a high affinity, bivalent carcinoembryonic antigen (CEA)-specific antibody devoid of Fc-mediated effector functions. Its molecular design aims to (i) avoid preferential activation of regulatory T-cells vs. immune effector cells by removing CD25 binding; (ii) increase the therapeutic index of IL-2 therapy by (a) preferential retention at the tumor by having a lower dissociation rate from CEA-expressing cancer cells vs. IL-2R-expressing cells, (b) avoiding any FcγR-binding and Fc effector functions and (c) reduced binding to endothelial cells expressing CD25; and (iii) improve the pharmacokinetics, and thus convenience of administration, of IL-2. The crystal structure of the IL2v-IL-2Rßγ complex was determined and CEA-IL2v activity was assessed using human immune effector cells. Tumor targeting was investigated in tumor-bearing mice using 89Zr-labeled CEA-IL2v. Efficacy studies were performed in (a) syngeneic mouse models as monotherapy and combined with anti-PD-L1, and in (b) xenograft mouse models in combination with ADCC-mediating antibodies. CEA-IL2v binds to CEA with pM avidity but not to CD25, and consequently did not preferentially activate Tregs. In vivo, CEA-IL2v demonstrated superior pharmacokinetics and tumor targeting compared with a wild-type IL-2-based CEA immunocytokine (CEA-IL2wt). CEA-IL2v strongly expanded NK and CD8+ T cells, skewing the CD8+:CD4+ ratio toward CD8+ T cells both in the periphery and in the tumor, and mediated single agent efficacy in syngeneic MC38-CEA and PancO2-CEA models. Combination with trastuzumab, cetuximab and imgatuzumab, all of human IgG1 isotype, resulted in superior efficacy compared with the monotherapies alone. Combined with anti-PD-L1, CEA-IL2v mediated superior efficacy over the respective monotherapies, and over the combination with an untargeted control immunocytokine. These preclinical data support the ongoing clinical investigation of the cergutuzumab amunaleukin immunocytokine with abolished CD25 binding for the treatment of CEA-positive solid tumors in combination with PD-L1 checkpoint blockade and ADCC competent antibodies.

Development of [11C]vemurafenib employing a carbon-11 carbonylative Stille coupling and preliminary evaluation in mice bearing melanoma tumor xenografts.

Over the last decade kinase inhibitors have witnessed tremendous growth as anti-cancer drugs. Unfortunately, despite their promising clinical successes, a large portion of patients does not benefit from these targeted therapeutics. Vemurafenib is a serine/threonine kinase inhibitor approved for the treatment of melanomas specifically expressing the BRAFV600E mutation. The aim of this study was to develop vemurafenib as PET tracer to determine its potential for identification of tumors sensitive to vemurafenib treatment. Therefore, vemurafenib was labeled with carbon-11 and analyzed for its tumor targeting potential in melanoma xenografts Colo829 (BRAFV600E) and MeWo (BRAFwt) using autoradiography on tissue sections, in vitro tumor cell uptake studies and biodistribution studies in xenografted athymic nu/nu mice. [11C]vemurafenib was synthesized in 21 ± 4% yield (decay corrected, calculated from [11C]CO) in > 99% radiochemical purity and a specific activity of 55 ± 18 GBq/µmol. Similar binding of [11C]vemurafenib was shown during autoradiography and cellular uptake studies in both cell lines. Plasma metabolite analysis demonstrated > 95% intact [11C]vemurafenib in vivo at 45 minutes after injection, indicating excellent stability. Biodistribution studies confirmed the in vitro results, showing similar tumor-to-background ratios in both xenografts models. These preliminary results suggest that identification of BRAFV600E mutations in vivo using PET with [11C]vemurafenib will be challenging.

A Novel Platinum(II)-Based Bifunctional ADC Linker Benchmarked Using 89Zr-Desferal and Auristatin F-Conjugated Trastuzumab.

Greater control is desirable in the stochastic conjugation technology used to synthesize antibody-drug conjugates (ADC). We have shown recently that a fluorescent dye can be stably conjugated to a mAb using a bifunctional platinum(II) linker. Here, we describe the general applicability of this novel linker technology for the preparation of stable and efficacious ADCs. The ethylenediamine platinum(II) moiety, herein called Lx, was coordinated to Desferal (DFO) or auristatin F (AF) to provide storable "semifinal" products, which were directly conjugated to unmodified mAbs. Conjugation resulted in ADCs with unimpaired mAb-binding characteristics, DAR in the range of 2.5 to 2.7 and approximately 85% payload bound to the Fc region, presumably to histidine residues. To evaluate the in vivo stability of Lx and its effect on pharmacokinetics and tumor targeting of an ADC, Lx-DFO was conjugated to the HER2 mAb trastuzumab, followed by radiolabeling with 89Zr. Trastuzumab-Lx-DFO-89Zr was stable in vivo and exhibited pharmacokinetic and tumor-targeting properties similar to parental trastuzumab. In a xenograft mouse model of gastric cancer (NCI-N87) or an ado-trastuzumab emtansine-resistant breast cancer (JIMT-1), a single dose of trastuzumab-Lx-AF outperformed its maleimide benchmark trastuzumab-Mal-AF and FDA-approved ado-trastuzumab emtansine. Overall, our findings show the potential of the Lx technology as a robust conjugation platform for the preparation of anticancer ADCs. Cancer Res; 77(2); 257-67. ©2016 AACR.

Development of novel ADCs: conjugation of tubulysin analogues to trastuzumab monitored by dual radiolabeling.

Tubulysins are highly toxic tubulin-targeting agents with a narrow therapeutic window that are interesting for application in antibody-drug conjugates (ADC). For full control over drug-antibody ratio (DAR) and the effect thereof on pharmacokinetics and tumor targeting, a dual-labeling approach was developed, wherein the drug, tubulysin variants, and the antibody, the anti-HER2 monoclonal antibody (mAb) trastuzumab, are radiolabeled. (131)I-radioiodination of two synthetic tubulysin A analogues, the less potent TUB-OH (IC50 > 100 nmol/L) and the potent TUB-OMOM (IC50, ~1 nmol/L), and their direct covalent conjugation to (89)Zr-trastuzumab were established. Radioiodination of tubulysins was 92% to 98% efficient and conversion to N-hydroxysuccinimide (NHS) esters more than 99%; esters were isolated in an overall yield of 68% ± 5% with radiochemical purity of more than 99.5%. Conjugation of (131)I-tubulysin-NHS esters to (89)Zr-trastuzumab was 45% to 55% efficient, resulting in ADCs with 96% to 98% radiochemical purity after size-exclusion chromatography. ADCs were evaluated for their tumor-targeting potential and antitumor effects in nude mice with tumors that were sensitive or resistant to trastuzumab, using ado-trastuzumab emtansine as a reference. ADCs appeared stable in vivo. An average DAR of 2 and 4 conferred pharmacokinetics and tumor-targeting behavior similar to parental trastuzumab. Efficacy studies using single-dose TUB-OMOM-trastuzumab (DAR 4) showed dose-dependent antitumor effects, including complete tumor eradications in trastuzumab-sensitive tumors in vivo. TUB-OMOM-trastuzumab (60 mg/kg) displayed efficacy similar to ado-trastuzumab emtansine (15 mg/kg) yet more effective than trastuzumab. Our findings illustrate the potential of synthetic tubulysins in ADCs for cancer treatment.