Actively personalized cancer vaccines--the step into clinical application.

Cancer vaccine development enters a new phase of innovation based on the development of modern sequencing technologies and novel RNA-based synthetic drug formats which enable the analysis and therapeutic targeting of every patient's tumor genome. By applying and combining these innovations, we have brought the concept of "actively personalized cancer vaccines" to clinical testing. Synthetic RNA is used as the drug format, allowing affordable, individual "on demand" manufacturing of tumor-optimized vaccines.

In vivo molecular imaging with cetuximab, an anti-EGFR antibody, for prediction of response in xenograft models of human colorectal cancer.

BACKGROUND AND STUDY AIMS: Molecular imaging has mainly been studied for detection of lesions using diagnostic probes. The aim of the current trial was to evaluate in vivo confocal laser endomicroscopy (CLE) with cetuximab, an antibody targeting the epidermal growth factor receptor (EGFR), for detection and moreover early prediction of response to molecular chemotherapy in models of human colorectal cancer (CRC). METHODS: Xenografts with cetuximab-sensitive (HT29) and cetuximab-resistant (SW620) human CRC cell lines were induced in 44 mice. CLE was performed 48 h after injection of a fluorescently labelled cetuximab test dose, and compared with isotype antibody or untreated controls on d0, and d30 (HT29) or d15 (SW620). Initial fluorescence intensity was examined in relation to clinical readouts (tumor growth, thriving, mortality) during cetuximab treatment vs. controls. Results were validated in vivo with wide-field molecular imaging in three HT29 mice and ex vivo using fluorescence-activated cell sorting (FACS) and immunohistochemistry. RESULTS: All HT29 xenografts showed specific fluorescence in vivo after cetuximab injection on d0 and d30. Fluorescence at d0 was significantly stronger in cetuximab-treated HT29 tumors than in HT29 controls (P = 0.0017) or cetuximab-treated SW620 tumors (P = 0.0027), and accorded with significantly slower tumor progression (P = 0.0009), better overall survival (P = 0.02), and better physical condition (P < 0.0001). Cetuximab sensitivity could be predicted from fluorescence intensity at d0 with high positive predictive value. CONCLUSIONS: Molecular CLE was for the first time linked to early prediction of response to targeted therapy in models of human CRC. Therapeutic antibodies can be used as molecular beacons in CLE and wide-field techniques. These results may indicate a promising principle for early patient stratification.

Selective uptake of naked vaccine RNA by dendritic cells is driven by macropinocytosis and abrogated upon DC maturation.

Even though it is known for more than one decade that antigen-encoding RNA can deliver antigenic information to induce antigen-specific immunity against cancer, the nature and mechanism of RNA uptake have remained enigmatic. In this study, we investigated the pharmacokinetics of naked RNA administered into the lymph node. We observed that RNA is rapidly and selectively uptaken by lymph node dendritic cells (DCs). Furthermore, in vitro and in vivo studies revealed that the efficient internalization of RNA by human and murine DCs is primarily driven by macropinocytosis. Selective inhibition of macropinocytosis by compounds or as a consequence of DC maturation abrogated RNA internalization and delivery of encoded antigens. Our findings imply that bioavailability of recombinant RNA vaccines in vivo highly depends on the density and the maturation stage of DCs at the administration site and are of importance for the design of RNA-based clinical immunotherapy protocols.

Phosphorothioate cap analogs increase stability and translational efficiency of RNA vaccines in immature dendritic cells and induce superior immune responses in vivo.

Vaccination with in vitro transcribed RNA coding for tumor antigens is considered a promising approach for cancer immunotherapy and has already entered human clinical testing. One of the basic objectives for development of RNA as a drug is the optimization of immunobioavailability of the encoded antigen in vivo. By analyzing the effect of different synthetic 5' mRNA cap analogs on the kinetics of the encoded protein, we found that m(2)(7,2'-O)Gpp(S)pG (beta-S-ARCA) phosphorothioate caps, in particular the D1 diastereoisomer, profoundly enhance RNA stability and translational efficiency in immature but not mature dendritic cells. Moreover, in vivo delivery of the antigen as beta-S-ARCA(D1)-capped RNA species is superior for protein expression and for efficient priming and expansion of naïve antigen-specific T cells in mice. Our findings establish 5' mRNA cap analogs as yet another module for tuning immunopharmacological properties of recombinant antigen-encoding RNA for vaccination purposes.