Recombinant measles viruses are currently tested in clinical trials as oncolytic agent to be applied in cancer therapy. Contrary to their use as vaccine where 10 3 infectious virus particles per dose are needed, for cancer therapy 10 9 virus particles should be provided per dose. This leads to other challenges for the production process when compared to vaccine production. This study presents measles virus stability with regard to conditions during production and storage of the virus. Relevant process parameters such as temperature (4-37°C), pH (pH 4-11), conductivity (1.5 to 137.5 mS cm ) and oxygen partial pressure were analyzed. The infectivity of measles virus particles decreased highly at 37 and 32°C, while at 22 and 4°C it remained stable for several hours or even days, respectively. The thermal inactivation reactions followed first order kinetics and the thermodynamic parameters enthalpy and entropy were estimated. Towards changes in pH measles virus particles were very sensitive, while no inactivation could be observed with varying conductivity. Measles virus incubation at an oxygen partial pressure of 100% did not lead to any loss of infectivity. The results show which parameters should be considered and controlled strongly in the production process to further raise measles virus yields for the high amount needed in cancer therapy approaches.

Measles virus (MV) with attenuated pathogenicity has potential as oncolytic agent. However, the clinical translation of this therapy concept has one major hurdle: the production of sufficient amounts of infectious oncolytic MV particles. The current study describes oncolytic MV production in Vero cells grown on microcarrier using serum-free medium. The impact of the number of harvests, cell concentration at infection (CCI), multiplicity of infection (MOI), and temperature on MV production was determined in different production scales/systems (static T-flasks, dynamic spinner, and bioreactor system) and modes (batch, repeated-batch, and perfusion). Cell growth, metabolic, and production kinetics were analyzed. It was found that the number of harvests had the strongest positive impact on MV yield in each production scale, and that high temperatures affected MV yield adversely. Moderate MV titers were produced in T- and spinner flasks at 37°C (∼107 TCID50 mL−1, where TCID50 is tissue culture infective doses 50%), but stirred tank reactor (STR) MV production at 37°C yielded up to 10 000-fold lower MV titers. In contrast, at lower temperatures (32°C, 27°C), 1.4 × 107 TCID50 mL−1 were achieved in the STR. Variations in MOI and CCI had almost no influence on MV production yield. The current study improves oncolytic MV production process understanding and identifies process bottlenecks for large-scale production