Abstract: An inventive drug product filling device for filling a liquid drug product into containers is disclosed. The drug filling device includes a drug product preparer configured for preparing the liquid drug product and a filling station configured for filling the liquid drug product into the containers. The filling station is fluidly coupled to the drug product preparer. A degasser is fluidly interposed between the drug product preparer and the filling station. The degasser has a membrane configured for at least partially separating off gas from the liquid drug product. Methods of (i) filling a liquid drug product into containers, (ii) increasing the accuracy of the filling weight of a liquid drug product in a container, (iii) increasing the stability oxygen-sensitive active pharmaceutical ingredient in a liquid drug product, and (iv) reducing polysorbate aggregate formation in a liquid drug product are also disclosed.