89Zr-immunoPET-guided selection of a CD33xIL15 fusion protein optimized for antitumor immune cell activation and in vivo tumour retention in acute myeloid leukaemia.

PURPOSE: Immune cells are capable of eliminating leukemic cells, as evidenced by outcomes in hematopoietic cell transplantation (HCT). However, patients who fail induction therapy will not benefit from HCT due to their minimal residual disease (MRD) status. Thus, we aimed to develop an immunomodulatory agent to reduce MRD by activating immune effector cells in the presence of leukaemia cells via a novel fusion protein that chimerises two clinically tolerated biologics: a CD33 antibody and the IL15Ra/IL15 complex (CD33xIL15). METHODS: We generated a set of CD33xIL15 fusion protein constructs with varying configurations and identified those with the best in vitro AML-binding, T cell activation, and NK cell potentiation. Using 89Zr-immunoPET imaging we then evaluated the biodistribution and in vivo tumour retention of the most favourable CD33xIL15 constructs in an AML xenograft model. Ex vivo biodistribution studies were used to confirm the pharmacokinetics of the constructs. RESULTS: Two of the generated fusion proteins, CD33xIL15 (N72D) and CD33xIL15wt, demonstrated optimal in vitro behaviour and were further evaluated in vivo. These studies revealed that the CD33xIL15wt candidate was capable of being retained in the tumour for as long as its parental CD33 antibody, Lintuzumab (13.9 ± 3.1%ID/g vs 18.6 ± 1.1%ID/g at 120 h). CONCLUSION: This work demonstrates that CD33xIL15 fusion proteins are capable of targeting leukemic cells and stimulating local T cells in vitro and of concentrating in the tumour in AML xenografts. It also highlights the importance of 89Zr-immunoPET to guide the development and selection of tumour-targeted antibody-cytokine fusion proteins.

PARP-Targeted Auger Therapy in p53 Mutant Colon Cancer Xenograft Mouse Models.

Despite Auger electrons being highly appealing due to their short-range and high linear energy transfer to surrounding tissues, the progress in the field has been limited due to the challenge in delivering a therapeutic dose within the close proximity of cancer cell's DNA. Here, we demonstrate that the PARP inhibitor 123I-MAPi is a viable agent for the systemic administration and treatment of p53 mutant cancers. Significantly, minimal off-site toxicity was observed in mice administered with up to 74 MBq of 127I-PARPi. Taken together, these results lay the foundation for future clinical evaluation and broader preclinical investigations. By harnessing the scaffold of the PARP inhibitor Olaparib, we were able to deliver therapeutic levels of Auger radiation to the site of human colorectal cancer xenograft tumors after systemic administration. In-depth toxicity studies analyzed blood chemistry levels and markers associated with specific organ toxicity. Finally, p53+/+ and p53-/- human colorectal cancer cell lines were evaluated for the ability of 123I-MAPi to induce tumor growth delay. Toxicity studies demonstrate that both 123I-MAPi and its stable isotopologue, 127I-PARPi, have no significant off-site toxicity when administered systemically. Analysis following 123I-MAPi treatment confirmed its ability to induce DNA damage at the site of xenograft tumors when administered systemically. Finally, we demonstrate that 123I-MAPi generates a therapeutic response in p53-/-, but not p53+/+, subcutaneous xenograft tumors in mouse models. Taken together, these results represent the first example of a PARP Auger theranostic agent capable of delivering a therapeutic dose to xenograft human colorectal cancer tumors upon systemic administration without causing significant toxicity to surrounding mouse organs. Moreover, it suggests that a PARP Auger theranostic can act as a targeted therapeutic for cancers with mutated p53 pathways. This landmark goal paves the way for clinical evaluation of 123I-MAPi for pan cancer therapeutics.

Interrogating the Theranostic Capacity of a MUC16-Targeted Antibody for Ovarian Cancer.

Aberrantly expressed glycans on mucins such as mucin-16 (MUC16) are implicated in the biology that promotes ovarian cancer (OC) malignancy. Here, we investigated the theranostic potential of a humanized antibody, huAR9.6, targeting fully glycosylated and hypoglycosylated MUC16 isoforms. Methods: In vitro and in vivo targeting of the diagnostic radiotracer [89Zr]Zr-DFO-huAR9.6 was investigated via binding experiments, immuno-PET imaging, and biodistribution studies on OC mouse models. Ovarian xenografts were used to determine the safety and efficacy of the therapeutic version, [177Lu]Lu-CHX-A″-DTPA-huAR9.6. Results: In vivo uptake of [89Zr]Zr-DFO-huAR9.6 supported in vitro-determined expression levels: high uptake in OVCAR3 and OVCAR4 tumors, low uptake in OVCAR5 tumors, and no uptake in OVCAR8 tumors. Accordingly, [177Lu]Lu-CHX-A″-DTPA-huAR9.6 displayed strong antitumor effects in the OVCAR3 model and improved overall survival in the OVCAR3 and OVCAR5 models in comparison to the saline control. Hematologic toxicity was transient in both models. Conclusion: PET imaging of OC xenografts showed that [89Zr]Zr-DFO-huAR9.6 delineated MUC16 expression levels, which correlated with in vitro results. Additionally, we showed that [177Lu]Lu-CHX-A″-DTPA-huAR9.6 displayed strong antitumor effects in highly MUC16-expressing tumors. These findings demonstrate great potential for 89Zr- and 177Lu-labeled huAR9.6 as theranostic tools for the diagnosis and treatment of OC.

NaV1.7 targeted fluorescence imaging agents for nerve identification during intraoperative procedures.

Surgeries and trauma result in traumatic and iatrogenic nerve damage that can result in a debilitating condition that approximately affects 189 million individuals worldwide. The risk of nerve injury during oncologic surgery is increased due to tumors displacing normal nerve location, blood turbidity, and past surgical procedures, which complicate even an experienced surgeon's ability to precisely locate vital nerves. Unfortunately, there is a glaring absence of contrast agents to assist surgeons in safeguarding vital nerves. To address this unmet clinical need, we leveraged the abundant expression of the voltage-gated sodium channel 1.7 (NaV1.7) as an intraoperative marker to access peripheral nerves in vivo, and visualized nerves for surgical guidance using a fluorescently-tagged version of a potent NaV1.7-targeted peptide, Tsp1a, derived from a Peruvian tarantula. We characterized the expression of NaV1.7 in sensory and motor peripheral nerves across mouse, primate, and human specimens and demonstrated universal expression. We synthesized and characterized a total of 10 fluorescently labeled Tsp1a-peptide conjugates to delineate nerves. We tested the ability of these peptide-conjugates to specifically accumulate in mouse nerves with a high signal-to-noise ratio in vivo. Using the best-performing candidate, Tsp1a-IR800, we performed thyroidectomies in non-human primates and demonstrated successful demarcation of the recurrent laryngeal and vagus nerves, which are commonly subjected to irreversible damage. The ability of Tsp1a to enhance nerve contrast during surgery provides opportunities to minimize nerve damage and revolutionize standards of care across various surgical specialties.

Noninvasive Diagnostic Method to Objectively Measure Olfaction and Diagnose Smell Disorders by a Molecularly Targeted Fluorescence Imaging Agent.

Despite the recent advances in understanding the mechanisms of olfaction, no tools are currently available to noninvasively identify loss of smell. Because of the substantial increase in patients presenting with coronavirus disease 2019-related loss of smell, the pandemic has highlighted the urgent need to develop quantitative methods. Methods: Our group investigated the use of a novel fluorescent probe named Tsp1a-IR800P as a tool to diagnose loss of smell. Tsp1a-IR800P targets sodium channel 1.7, which plays a critical role in olfaction by aiding the signal propagation to the olfactory bulb. Results: Intuitively, we have identified that conditions leading to loss of smell, including chronic inflammation and coronavirus disease 2019, correlate with the downregulation of sodium channel 1.7 expression in the olfactory epithelium, both at the transcript and at the protein levels. We demonstrated that lower Tsp1a-IR800P fluorescence emissions significantly correlate with loss of smell in live animals-thus representing a potential tool for its semiquantitative assessment. Currently available methods rely on delayed subjective behavioral studies. Conclusion: This method could aid in significantly improving preclinical and clinical studies by providing a way to objectively diagnose loss of smell and therefore aid the development of therapeutic interventions.

89Zr-DFO-Isatuximab for CD38-Targeted ImmunoPET Imaging of Multiple Myeloma and Lymphomas.

Multiple myeloma (MM) is the second most prevalent hematological malignancy. It remains incurable despite the availability of novel therapeutic approaches, marking an urgent need for new agents for noninvasive targeted imaging of MM lesions. CD38 has proven to be an excellent biomarker due to its high expression in aberrant lymphoid and myeloid cells relative to normal cell populations. Using isatuximab (Sanofi), the latest FDA-approved CD38-targeting antibody, we have developed Zirconium-89(89Zr)-labeled isatuximab as a novel immunoPET tracer for the in vivo delineation of MM and evaluated the extension of its applicability to lymphomas. In vitro studies validated the high binding affinity and specificity of 89Zr-DFO-isatuximab for CD38. PET imaging demonstrated the high performance of 89Zr-DFO-isatuximab as a targeted imaging agent to delineate tumor burden in disseminated models of MM and Burkitt's lymphoma. Ex vivo biodistribution studies confirmed that high accumulations of the tracer in bone marrow and bone skeleton correspond to specific disease lesions as they are reduced to background in blocking and healthy controls. This work demonstrates the promise of 89Zr-DFO-isatuximab as an immunoPET tracer for CD38-targeted imaging of MM and certain lymphomas. More importantly, its potential as an alternative to 89Zr-DFO-daratumumab holds great clinical relevance.

Polyethylene Glycol 3350 (PEG 3350) as a Practical Vehicle for Rapid Reconstitution of PARPi-FL Formulations for Clinical Use.

PARPi-FL is a molecularly specific fluorescent agent that targets poly ADP-ribose polymerase 1, a DNA repair enzyme overexpressed in the nuclei of tumor cells. This imaging agent is being investigated in a clinical trial (NCT03085147) for the detection of oral cancer. The PARPi-FL mouthwash formulation currently being used in the phase I/II clinical trial comprises 1,000 nM of PARPi-FL dissolved first in 4.5 ml of polyethylene glycol (PEG) 300 and then in 9.5 ml of water. This formulation requires a 2-step process that can be cumbersome for routine clinical use. To minimize errors and simplify the formulation process, we have developed a new one-step formulation, which requires only the direct addition of water into a vial containing a mixture of the PARPi-FL and PEG 3350, which is also a powder. In a series of analytical and preclinical studies, we demonstrate that the new formulation of PARPi-FL is stable over 365 days, sustains its characteristics, and performs similar to the previous formulation. Moving forward, the new formulation of the PARPi-FL will be used for patients accrued in the phase II clinical trial.

EGFR-Targeted ImmunoPET of UMUC3 Orthotopic Bladder Tumors.

PURPOSE: Immuno-positron emission tomography (immunoPET) combines the specificity of an antibody with the sensitivity of PET to image dysregulated pathways in cancer. This study examines the performance of immunoPET using the radioimmunoconjugate [89Zr]Zr-DFO-Panitumumab to detect epidermal growth factor receptor (EGFR) expression in an orthotopic model of bladder cancer (BCa). PROCEDURES: Expression and quantification of EGFR receptors were confirmed in four different BCa cell lines. Binding assays validated [89Zr]Zr-DFO-Panitumumab specificity for EGFR-expressing UMUC3 BCa cells. Subcutaneous and orthotopic UMUC3 xenografts were then used for PET imaging and ex vivo biodistribution of the radioimmunoconjugate. Control cohorts included non-tumor mice, 89Zr-labeled non-specific IgG, and blocking experiments. RESULTS: [89Zr]Zr-DFO-Panitumumab binds specifically to EGFR-expressing UMUC3 cells with a Bmax value of 5.9 × 104 EGFRs/cell in vitro. ImmunoPET/CT images show localization of the antibody in subcutaneous UMUC3 xenografts and murine bladder tumors. In the orthotopic model, the immunoPET signal correlates with the respective tumor volume. Ex vivo biodistribution analysis further confirmed imaging results. CONCLUSION: The preclinical data presents a proof of concept for utilizing EGFR-targeted immunoPET to image BCa with altered EGFR protein levels.

Non-invasive diagnostic method to objectively measure olfaction and diagnose smell disorders by molecularly targeted fluorescent imaging agent.

The sense of smell (olfaction) is one of the most important senses for animals including humans. Despite significant advances in the understanding mechanism of olfaction, currently, there are no objective non-invasive methods that can identify loss of smell. Covid-19-related loss of smell has highlighted the need to develop methods that can identify loss of olfaction. Voltage-gated sodium channel 1.7 (NaV1.7) plays a critical role in olfaction by aiding the signal propagation to the olfactory bulb. We have identified several conditions such as chronic inflammation and viral infections such as Covid-19 that lead to loss of smell correlate with downregulation of NaV1.7 expression at transcript and protein levels in the olfactory epithelium. Leveraging this knowledge, we have developed a novel fluorescent probe Tsp1a-IR800 that targets NaV1.7. Using fluorescence imaging we can objectively measure the loss of sense of smell in live animals non-invasively. We also demonstrate that our non-invasive method is semiquantitative because the loss of fluorescence intensity correlates with the level of smell loss. Our results indicate, that our probe Tsp1a-IR800, can objectively diagnose anosmia in animal and human subjects using infrared fluorescence. We believe this method to non-invasively diagnose loss of smell objectively is a significant advancement in relation to current methods that rely on highly subjective behavioral studies and can aid in studying olfaction loss and the development of therapeutic interventions.