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First-in-Human Imaging of Multiple Myeloma Using Copper-64-Labeled Daratumumab: Preliminary Results

Introduction: 18Fluoro-deoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is one of the most widely used imaging techniques to detect multiple myeloma (MM). Intracellular FDG uptake depicts in vivo metabolic activity, which can be seen in both malignant and non-malignant cells, resulting in limited sensitivity and specificity. Our group showed preclinically that tracing MM dissemination using a CD38-directed human antibody, daratumumab, that is radioconjugated with copper-64 via the chelator DOTA (64Cu-DOTA-Dara), led to improved sensitivity and specificity over that of FDG (Caserta et al, Blood 2018). Herein, we report the results of a Phase 1 trial (NCT#03311828) designed to 1) assess the safety and feasibility of 64Cu-DOTA-Dara PET/CT and 2) to evaluate and characterize the ability of 64Cu-DOTA-Dara to accurately detect or exclude MM lesions compared with FDG PET/CT.
 Methods: Patients with biopsy-proven MM and/or a plasmacytoma received an FDG PET/CT scan within 60 days of enrollment. On Day 0, patients were infused with unlabeled ("cold") Dara at one of four dose levels (0 mg, 10 mg, 45 mg, 95 mg) to optimize biodistribution of radioconjugated 64Cu-DOTA-Dara, especially in the liver and the spleen. Within 6 hours of unlabeled Dara administration, patients received 64Cu-DOTA-Dara at a dose of 13.63-16.68 mCi (~5 mg). Whole-body PET scans were obtained at 24 hours and at 48 hours (the latter scan encompassing known tumors). 64Cu-DOTA-Dara standardized uptake values (SUV) were evaluated in MM lesions and normal organs, which were then compared with values from standard FDG PET/CT. Biopsies were performed on accessible discordant lesions.
 Results: A total of 10 Dara-naïve patients were imaged. Patients were treated with 0 (n=3), 10 (n=3), 45 (n=3), or 95 mg (n=1) of unlabeled Dara. Four patients had newly diagnosed disease, one had biochemical relapse, one had a recurrent plasmacytoma by MRI, and four had possible recurrence by standard PET/CT. No significant adverse events were observed from either cold or 64Cu-DOTA-Dara. With the exception of the one patient with a recurrent plasmacytoma, radiolabeled antibody was eliminated from systemic circulation in subjects analyzed at the first three dose levels within 30 min post injection. In the patient with a recurrent plasmacytoma, the radiolabeled antibody was elevated in the blood for over two days.
 One newly diagnosed patient had extensive disease by FDG PET and had a biopsy-proven target lesion in the sternum, which had an SUVmax of 14.7 on 64Cu-DOTA-Dara PET/CT vs. 3.3 onFDG PET/CT. A second biopsy from the same patient was taken from a discordant iliac crest lesion (positive for 64Cu-DOTA-Dara but negative for FDG PET/CT) that showed 20-30% MM cell infiltration. In another patient, an iliac crest lesion was 64Cu-DOTA-Dara positive and FDG-negative; biopsy revealed 6% plasmacytosis in the bone. A third patient had an FDG PET/CT positive pleural lesion with an SUVmax of 8.98 and negative on 64Cu-DOTA-Dara (Figure 1A). The lesion did not show recurrence upon biopsy. Furthermore, 64Cu-DOTA-Dara PET/CT yielded superior imaging of bone lesions in the calvarium (Figure 1B). Escalating doses of unlabeled Dara decreased liver and spleen uptake by 64Cu-DOTA-Dara.
 Conclusions: In this ongoing study, 64Cu-DOTA-Dara PET/CT imaging is to date safe and provides whole body imaging of MM. Further dose escalation of cold Dara (145 mg, 195 mg) is planned to optimize background interference. This modality has the potential to improve sensitivity and specificity over FDG PET/CT scanning in early-stage MM as well as in recurrent disease.
 
 
 
 Krishnan: Celgene, Janssen, Sanofi, BMS: Consultancy; Sutro BioPharma, zPredicta: Consultancy; Amgen, Takeda: Speakers Bureau; Celgene, Z Predicta: Other: Stock Ownership; Takeda: Research Funding. Palmer:Gilead Sciences: Consultancy. Rosenzweig:Celgene, Takeda: Speakers Bureau. Wu:ImaginAb, Inc.: Consultancy, Other: Board Member.
