A therapeutic preparation, and a process of using the preparation, for the control of tumour growth and infectious diseases. The preparation is an immobilized cytotoxic enzyme system which is carried by an insoluble substrate that is administered into the mammalian subject by injection or implantation. The preferred embodiment of the preparation uses a polymerized albumin carrier containing immobilized glucose oxidase and peroxidase. The immobilized enzyme system is prepared in the form of small particles that can be administered either by implantation or by injection into tumour-bearing mammals. To date, antibacterial activity has been demonstrated only in vitro. Intraperitoneal injection into rats bearing Novikoff hepatomas or into mice bearing B16-Fl melanomas or L1210 (Lymphoid) tumours has resulted in the selected killing of tumour tissues. Several daily administrations are required to achieve complete destruction of the tumour. Additionally, the preparation is also active as a stimulant of the specific immune response to neoplasia. Its effect on the immune system could be useful in the stimulation of the immune system in diseases where the action of the endogenous immune system is insufficient.