Abstract: The present disclosure generally pertains to in vivo drug development and delivery systems and methods. The systems include a hollow tubular assembly with a chamber for receiving and transmitting an ionizing substrate solution, and a structure to transmit non-radioactive ionizing radiation to the ionizing substrate solution. The resulting free radical drug is transferred directly into a patient treatment site through an applicator. The systems and methods described herein provide simple, inexpensive techniques for in vivo production of an optimal chemotherapeutic drug without the use of radioactive radiation and directly injecting the drug into the patient's tissue with very minimal systemic side-effects.