This thesis describes a general platform for the synthesis of radiolabelled antibody recruiting small molecules (R-ARMs) for combination radio and immune recruitment therapies. The novel trifunctional ARM was synthesized and radiolabelled with beta (lutetium-177) and alpha (actinium-225) emitting radionuclides in high yield. Biodistribution of the lutetium-ARM revealed rapid renal clearance and minimal uptake in non-target tissues with all organs and tissues containing less than 0.3 %ID/g by 24 hours post-injection. Having determined the pharmacokinetic properties of the ligand, a biodistribution study was performed to determine the targeting potential of the platform. Through the use of a validated bone targeted bisphosphonate, uptake in the arm and leg bones was achieved. Flow cytometry studies successfully demonstrated ARM and antibody dependent immune cell recruitment. Based on the promising results of the ARM in vitro and in vivo, the next step was to perform therapy studies.
In order to validate the novel R-ARM, an intratumoral (i.t.) strategy was developed through the preparation of a TCO-bovine serum albumin (BSA) derivative. This new chemical entity was used in both an aggregated and non-aggregated form to retain the R-ARM in the tumour after i.t. administration. Biodistribution showed high retention of the aggregated and non-aggregated BSA out to 120 hours with 167 ± 94 and 81 ± 32 %ID/g respectively remaining in the tumour. An autoradiography study revealed the after i.t. administration the aggregated material was localized in specific regions within the tumour compared to the non-aggregated material which diffused throughout. The aggregated material was used in a single and multi-dosing radiotherapy study in which the latter induced a statistically significant survival advantage compared to the control. One additional multi-dosing study was performed with the non-
aggregated material which resulted in the largest survival advantage to date. Intratumoral administration of TCO-BSA linked to the trifunctional tetrazine showed promising radiotherapy results and future work on dose optimization with lutetium and actinium is required prior to the combination R-ARM therapy.
In parallel, the efficacy of the unlabelled ARM linked to TCO-BSA was interrogated in preclinical models. The compound was administered i.t. three times per week in a breast cancer tumour model, and response to therapy monitored. The immunized group showed no survival advantage compared to the control group comprised of naïve animals. Biodistribution studies were performed to determine if TCO-BSA was accessible to the bloodstream following i.t. administration in both the aggregated and non-aggregated forms. Saline, aggregated or non-aggregated TCO-BSA were administered i.t. followed by the R-ARM. The results showed very low uptake in the tumour for all three groups, with minimal change in distribution from that of the native R-ARM. This suggests that after i.t. administration, the TCO-BSA was not available to molecules in the bloodstream or the concentration was insufficient to promote in vivo coupling. Further work on this component of the platform is needed before further ARM studies are performed. / Thesis / Doctor of Science (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/25928 |
| Date | January 2020 |
| Creators | Rathmann, Stephanie |
| Contributors | Valliant, John, Chemistry |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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