Sequential CAR T cell and targeted alpha immunotherapy in disseminated multiple myeloma.

Multiple myeloma (MM) is still an incurable disorder despite improved antibody and cellular therapies against different MM antigens. Single targeted antigens have so far been ineffective against MM with most patients relapsing after initial response. Hence, sequential immunotherapies directed at different targets are expected to perform better than monotherapy alone. Here, we optimized and established in preclinical studies the therapeutic rationale of using targeted alpha therapy (TAT) directed against CD38 antigen (225Ac-DOTA-daratumumab) with CAR T cell therapy directed at CS1 antigen in a systemic MM model. The sequential therapies compared CAR T therapy followed by TAT to TAT followed by CAR T therapy. CAR T cell monotherapy increased median survival from 49 days (d) in untreated controls to 71d with a modest improvement to 89d for 3.7 kBq of TAT given 14d later. When CAR T was followed by 7.4 kBq of TAT 29d later, sequential therapy increased median survival from 47d in untreated controls to 106d, compared to 68d for CAR T monotherapy. When CAR T therapy was followed by untargeted alpha immunotherapy using 7.4 kBq of 225Ac-DOTA-trastuzumab (anti-HER2) antibody 29d later, there was only a slight improvement in response over CAR T monotherapy demonstrating the role of tumor targeting. TAT (7.4 kBq) followed by CAR T therapy was also effective when CAR T therapy was delayed for 21d vs 14d or 28d post TAT, highlighting the importance of timing sequential therapies. Sequential targeted therapies using CS1 CAR T or 225Ac-DOTA-CD38 TAT in either order shows promise over monotherapies alone.

Antibody Targeted PET Imaging of 64Cu-DOTA-Anti-CEA PEGylated Lipid Nanodiscs in CEA Positive Tumors.

Lipid nanodiscs (LNDs), comprising a phospholipid bilayer encircled by two molecules of a recombinant membrane scaffold protein, can be targeted to tumors with covalently attached antibodies (Abs) or their fragments. Antibody attachment to click chemistry based PEGylated lipids on LNDs including DOTA allowed PET imaging with the positron emitter 64Cu. Carcinoembryonic antigen (CEA) positive tumors in CEA transgenic mice were chosen as a tumor target. Fab' fragments, that otherwise are rapidly cleared by the kidney due to their small size, were retained in circulation when conjugated to LNDs. Untargeted PET imaging of 64Cu-DOTA-LNDs revealed low tumor uptake (4-5% ID/g) in the range expected for the enhanced permeability retention (EPR) effect with high liver uptake (17-21% ID/g) indicating gut clearance. Fab' targeted LNDs showed little improvement over untargeted LNDs, but intact IgG targeted LNDs gave high tumor uptake (40% ID/g) with low liver (8% ID/g), demonstrating that tumor targeting with antibody conjugated LNDs is feasible.

Copper 64-labeled daratumumab as a PET/CT imaging tracer for multiple myeloma.

As a growing number of patients with multiple myeloma (MM) respond to upfront therapies while eventually relapsing in a time frame that is often unpredictable, attention has increasingly focused on developing novel diagnostic criteria to also account for disease dissemination. Positron emission tomography/computed tomography (PET/CT) is often used as a noninvasive monitoring strategy to assess cancer cell dissemination, but because the uptake of the currently used radiotracer 18fluorodeoxyglucose (18F-FDG) is a function of the metabolic activity of both malignant and nonmalignant cells, the results frequently lack sufficient specificity. Radiolabeled antibodies targeting MM tissue may detect disease irrespective of cell metabolism. Hence, we conjugated the clinically significant CD38-directed human antibody daratumumab (Darzalex [Dara]) to the DOTA chelator and labeled it with the positron-emitting radionuclide copper 64 (64Cu; 64Cu-DOTA-Dara). Here, we show that 64Cu-DOTA-Dara can efficiently bind CD38 on the surface of MM cells and was mainly detected in the bones associated with tumor in a MM murine model. We also show that PET/CT based on 64Cu-DOTA-Dara displays a higher resolution and specificity to detect MM cell dissemination than does 18F-FDG PET/CT and was even more sensitive than were bioluminescence signals. We therefore have supporting evidence for using 64Cu-DOTA-Dara as a novel imaging agent for MM.

Comparison of IL-2-antibody to IL-2-Fc with or without stereotactic radiation therapy in CEA immunocompetent mice with CEA positive tumors.

BACKGROUND: The potent immune effects of interleukin-2 (IL-2) for cancer therapy can be increased by genetic fusion of IL-2 to the Fc domain of an antibody (IL-2-Fc) or tumor targeted by genetic fusion to a whole antibody known as an immunocytokine (ICK). METHODS: An anti-CEA ICK (M5A-IL-2) was compared to an IL-2-Fc fusion protein using tumor therapy and PET imaging in CEA transgenic immunocompetent mice bearing CEA positive colon or breast tumors. Combination with stereotactic radiation therapy (SRT) was performed with either ICK or IL-2-Fc. RESULTS: ICK and IL-2-Fc had comparable antitumor effects in both tumor models, although ICK had higher tumor uptake and slower blood clearance than an IL-2-Fc. Analysis of IFNγ+ /CD8+ and FoxP3+ /CD4+ T cells revealed higher levels of IFNγ-producing CD8+ T cells in ICK treated mice versus more efficient Treg elimination in IL-2-Fc treated mice. No significant or lasting toxicity was detected for either agent. Combination therapies with SRT revealed comparable efficacy and induction of immune memory for both ICK and IL-2-Fc when mice were rechallenged post-therapy. CONCLUSIONS: IL-2-Fc had comparable antitumor efficacy to CEA-targeted M5A-IL-2 ICK, while both fusion proteins induced immune memory when combined with SRT. Differences in the therapeutic mechanisms of both agents were observed.

Yttrium-90 anti-CD25 BEAM conditioning for autologous hematopoietic cell transplantation in Peripheral T-cell lymphoma.

ABSTRACT: Peripheral T-cell lymphomas (PTCLs) have a poor prognosis with current treatments. High-dose chemotherapy followed by autologous hematopoietic cell transplant (AHCT) is used as a consolidation strategy after achieving clinical remission with first-line therapy, as well as in chemotherapy-sensitive relapse if allogeneic transplant is not an option. CD25 is a targetable protein often highly expressed in PTCLs. In this phase 1 clinical trial, we tested the addition of ß-emitting 90yttrium (90Y)-labeled chimeric anti-CD25 basiliximab (aTac) to BEAM (carmustine, etoposide, cytarabine, and melphalan) as conditioning for AHCT for patients with PTCL. Twenty-three AHCT-eligible patients were enrolled, and 20 received therapeutic 90Y-aTac-BEAM AHCT. Radiation doses of 0.4, 0.5, and 0.6 mCi/kg were tested. With no observed dose-limiting toxicities, 0.6 mCi/kg was deemed the recommended phase 2 dose. The most prevalent adverse effect, grade 2 mucositis, was experienced by 80% of patients. As of this report, 6 (30%) of the treated patients had died, 5 due to progressive disease and 1 due to multiple organ failure (median time of death, 17 months [range, 9-21]) after AHCT. Median follow-up was 24 months (range, 9-26) overall and 24 months (range, 13-26) for surviving patients. For patients who received therapeutic 90Y-aTac-BEAM AHCT, the 2-year progression-free and overall survival were 59% (95% confidence interval [CI], 34-77) and 68% (95% CI, 42-84), respectively. 90Y-aTac-BEAM appears to be safe as an AHCT conditioning regimen for PTCL, with no increased toxicity over the toxicities historically seen with BEAM alone in this patient population. This trial was registered at www.ClinicalTrials.gov as #NCT02342782.

Generation of IL-2-Fc-antibody conjugates by click chemistry.

BACKGROUND: Immunocytokines (ICKs) are antibody directed cytokines produced by genetic fusion of an antibody to a cytokine. METHODS: We now show that antibodies conjugated by click chemistry to interleukin-2 (IL-2)-Fc form fully active conjugates, and in one example, equivalent activity to a genetically produced ICK. RESULTS: An IL-2-Fc fusion protein was optimized for click chemistry at hinge cysteines using protein stabilizing IL-2 mutations at Lys35 and Cys125 and Fc hinge mutations at Cys142 and Cys148. The IL-2-Fc fusion protein with K35E and C125S mutations with 3 intact hinge cysteines, designated as IL-2-Fc Par, was selected based on its minimal tendency to aggregate. IL-2-Fc-antibody clicked conjugates retained high IL-2 activity and bound target antigens comparable to parent antibodies. An IL-2-Fc-anti-CEA click conjugate showed comparable anti-tumor activity to an anti-CEA-IL-2 ICK in immunocompetent CEA transgenic mice bearing CEA positive orthotopic breast tumors. Significant increases in IFNγ+ /CD8+ and decreases in FoxP3+ /CD4+ T-cells were found for the clicked conjugate and ICK therapies, suggesting a common mechanism of tumor reduction. CONCLUSION: The production of antibody targeted IL-2 therapy via a click chemistry approach is feasible with comparable activity to genetically produced ICKs with the added advantage of multiplexing with other monoclonal antibodies.

Pilot study of HER2 targeted 64 Cu-DOTA-tagged PET imaging in gastric cancer patients.

OBJECTIVE: Human epidermal growth factor receptor 2 (HER2) is an important biomarker for targeted gastric cancer (GC) immunotherapy. However, heterogeneous HER2 overexpression in GC, loss of HER2 expression during therapy, and inability to non-invasively identify HER2 overexpressing tumors impede effective targeting therapies. Improved HER2-specific functional imaging can address these challenges. Trastuzumab is a HER2-directed mAb to treat HER2 overexpressing cancers. The 64 Cu-DOTA-trastuzumab radiotracer is used to detect HER2+ metastatic breast cancer. We aimed to develop 64 Cu-DOTA-trastuzumab PET-CT to detect and characterize tumor uptake in HER2+ or - GC patients. METHODS: We conducted a single-arm phase II pilot study exploring the feasibility of 64 Cu-DOTA-trastuzumab for PET imaging of HER2 overexpressing GC compared to HER2 non-expressing tumors. Eight patients with biopsy-confirmed gastric adenocarcinoma were included. Immunohistochemistry was used to evaluate primary tumor biopsies for HER2 overexpression. Patients were injected with 45 mg of cold trastuzumab followed by 5 mg of 64 Cu-DOTA-trastuzumab. PET-CT scans were performed 24-48 h post radiotracer injection and compared to standard staging CT scans. RESULTS: We observed limited toxicity following 64 Cu-DOTA-trastuzumab injections. While there was uptake of the radiotracer in portions of HER2+ lesions, there was no statistically significant distinction between tumor and background by standardized uptake value analysis. CONCLUSION: Despite the potential of 64 Cu-DOTA-trastuzumab PET imaging of HER2+ metastatic breast cancer, a 5 mg dose of this radiotracer injected 24-48 h before imaging was insufficient to identify HER2+ GC. These results inform future GC imaging studies to optimize biomarker-targeted therapies based on dosage and timing for more clinically relevant imaging.

Multimodality PET and Near-Infrared Fluorescence Intraoperative Imaging of CEA-Positive Colorectal Cancer.

PURPOSE: Molecular imaging is a major diagnostic component for cancer management, enabling detection, staging of disease, targeting therapy, and monitoring the therapeutic response. The coordination of multimodality imaging techniques further enhances tumor localization. The development of a single agent for real-time non-invasive targeted positron emission tomography (PET) imaging and fluorescence guided surgery (FGS) will provide the next generation tool in the surgical management of cancer. PROCEDURES: The humanized anti-CEA M5A-IR800 "sidewinder" (M5A-IR800-SW) antibody-dye conjugate was designed with a NIR 800 nm dye incorporated into a PEGylated linker and conjugated with the metal chelate p-SCN-Bn-deferoxamine (DFO) for zirconium-89 PET imaging (89Zr, half-life 78.4 h). The dual-labeled 89Zr-DFO-M5A-SW-IR800 was evaluated for near infrared (NIR) fluorescence imaging, PET/MRI imaging, terminal tissue biodistribution, and blood clearance in a human colorectal cancer LS174T xenograft mouse model. RESULTS: The 89Zr-DFO-M5A-SW-IR800 NIR fluorescence imaging showed high tumor targeting with normal liver uptake. Serial PET/MRI imaging was performed at 24 h, 48 h, and 72 h and showed tumor localization visible at 24 h that persisted throughout the experiment. However, the PET scans showed higher activity for the liver than the tumor, compared to the NIR fluorescence imaging. This difference is an important finding as it quantifies the expected difference due to the sensitivity and depth of penetration between the 2 modalities. CONCLUSIONS: This study demonstrates the potential of a pegylated anti-CEA M5A-IR800-Sidewinder for NIR fluorescence/PET/MR multimodality imaging for intraoperative fluorescence guided surgery.

First-In-Human Pilot PET Immunoimaging Study of 64Cu-Anti-Carcinoembryonic Antigen Monoclonal Antibody (hT84.66-M5A) in Patients with Carcinoembryonic Antigen-Producing Cancers.

Background: PET imaging using radiolabeled immunoconstructs shows promise in cancer detection and in assessing tumor response to therapies. The authors report the first-in-human pilot study evaluating M5A, a humanized anti-carcinoembryonic antigen (CEA) monoclonal antibody (mAb), radiolabeled with 64Cu in patients with CEA-expressing malignancies. The purpose of this pilot study was to identify the preferred patient population for further evaluation of this agent in an expanded trial. Methods: Patients with CEA-expressing primary or metastatic cancer received 64Cu-DOTA-hT84.66-M5A with imaging performed at 1 and 2 days postinfusion. 64Cu-DOTA-hT84.66-M5A PET scan findings were correlated with CT, MRI, and/or FDG PET scans and with histopathologic findings from planned surgery or biopsy performed postscan. Results: Twenty patients received 64Cu-DOTA-hT84.66-M5A. Twelve patients demonstrated positive images, which were confirmed in 10 patients as tumor by standard-of-care (SOC) imaging, biopsy, or surgical findings. Four of the 8 patients with negative imaging were confirmed as true negative, with the remaining 4 patients having disease demonstrated by SOC imaging or surgery. All 5 patients with locally advanced rectal cancer underwent planned biopsy or surgery after 64Cu-DOTA-hT84.66-M5A imaging (4 patients imaged 6-8 weeks after completing neoadjuvant chemotherapy and radiation therapy) and demonstrated a high concordance between biopsy findings and 64Cu-DOTA-hT84.66-M5A PET scan results. Three patients demonstrated positive uptake at the primary site later confirmed by biopsy and at surgery as residual disease. Two patients with negative scans each demonstrated complete pathologic response. In 5 patients with medullary thyroid cancer, 64Cu-DOTA-hT84.66-M5A identified disease not seen on initial CT scans in 3 patients, later confirmed to be disease by subsequent surgery or MRI. Conclusions: 64Cu-DOTA-hT84.66-M5A demonstrates promise in tumor detection, particularly in patients with locally advanced rectal cancer and medullary thyroid cancer. A successor trial in locally advanced rectal cancer has been initiated to further evaluate this agent's ability to define tumor extent before and assess disease response after neoadjuvant chemotherapy and radiotherapy. clinical trial.gov (NCT02293954).

Improved Tumor Responses with Sequential Targeted α-Particles Followed by Interleukin 2 Immunocytokine Therapies in Treatment of CEA-Positive Breast and Colon Tumors in CEA Transgenic Mice.

Targeted α-therapy (TAT) delivers high-linear-transfer-energy α-particles to tumors with the potential to generate tumor immune responses that may be augmented by antigen-targeted immunotherapy. Methods: This concept was evaluated in immunocompetent carcinoembryonic antigen (CEA) transgenic mice bearing CEA-positive mammary or colon tumors. Tumors were targeted with humanized anti-CEA antibody M5A labeled with 225Ac for its 10-d half-life and emission of 4 α-particles, as well as being targeted with the immunocytokine M5A-interleukin 2. Results: A dose response (3.7, 7.4, and 11.1 kBq) to TAT only, for orthotopic CEA-positive mammary tumors, was observed, with a tumor growth delay of 30 d and an increase in median survival from 20 to 36 d at the highest dose. Immunocytokine (4 times daily) monotherapy gave a tumor growth delay of 20 d that was not improved by addition of 7.4 kBq of TAT 5 d after the start of immunocytokine. However, TAT (7.4 kBq) followed by immunocytokine 10 d later led to a tumor growth delay of 38 d, with an increase in median survival to 45 d. Similar results were seen for TAT followed by immunocytokine at 5 versus 10 d. When a similar study was performed with subcutaneously implanted CEA-positive MC38 colon tumors, TAT (7.4 kBq) monotherapy gave an increase in median survival from 29 to 42 d. The addition of immunocytokine 10 d after 7.4 kBq of TAT increased median survival to 57 d. Immunophenotyping showed increased tumor-infiltrating interferon-γ-positive, CD8-positive T cells and an increased ratio of these cells to Foxp3-positive, CD4-positive regulatory T cells with sequential therapy. Immunohistochemistry confirmed there was an increase in tumor-infiltrating CD8-positive T cells in the sequential therapy group, strongly suggesting that immunocytokine augmented TAT can lead to an immune response that improves tumor therapy. Conclusion: Low-dose (7.4 kBq) TAT followed by a 4-dose immunocytokine regimen 5 or 10 d later gave superior tumor reductions and survival curves compared with either monotherapy in breast and colon cancer tumor models. Reversing the order of therapy to immunocytokine followed by TAT 5 d later was equivalent to either monotherapy in the breast cancer model.

Biodistribution of Intra-Arterial and Intravenous Delivery of Human Umbilical Cord Mesenchymal Stem Cell-Derived Extracellular Vesicles in a Rat Model to Guide Delivery Strategies for Diabetes Therapies.

Umbilical cord mesenchymal stem cell-derived extracellular vesicles (UC-MSC-EVs) have become an emerging strategy for treating various autoimmune and metabolic disorders, particularly diabetes. Delivery of UC-MSC-EVs is essential to ensure optimal efficacy of UC-MSC-EVs. To develop safe and superior EVs-based delivery strategies, we explored nuclear techniques including positron emission tomography (PET) to evaluate the delivery of UC-MSC-EVs in vivo. In this study, human UC-MSC-EVs were first successfully tagged with I-124 to permit PET determination. Intravenous (I.V.) and intra-arterial (I.A.) administration routes of [124I]I-UC-MSC-EVs were compared and evaluated by in vivo PET-CT imaging and ex vivo biodistribution in a non-diabetic Lewis (LEW) rat model. For I.A. administration, [124I]I-UC-MSC-EVs were directly infused into the pancreatic parenchyma via the celiac artery. PET imaging revealed that the predominant uptake occurred in the liver for both injection routes, and further imaging characterized clearance patterns of [124I]I-UC-MSC-EVs. For biodistribution, the uptake (%ID/gram) in the spleen was significantly higher for I.V. administration compared to I.A. administration (1.95 ± 0.03 and 0.43 ± 0.07, respectively). Importantly, the pancreas displayed similar uptake levels between the two modalities (0.20 ± 0.06 for I.V. and 0.24 ± 0.03 for I.A.). Therefore, our initial data revealed that both routes had similar delivery efficiency for [124I]I-UC-MSC-EVs except in the spleen and liver, considering that higher spleen uptake could enhance immunomodulatory application of UC-MSC-EVs. These findings could guide the development of safe and efficacious delivery strategies for UC-MSC-EVs in diabetes therapies, in which a minimally invasive I.V. approach would serve as a better delivery strategy. Further confirmation studies are ongoing.

Use of 64Cu-DOTA-Trastuzumab PET to Predict Response and Outcome of Patients Receiving Trastuzumab Emtansine for Metastatic Breast Cancer: A Pilot Study.

We hypothesized that functional imaging with 64Cu-DOTA-trastuzumab PET/CT would predict the response to the antibody-drug conjugate trastuzumab-emtansine (T-DM1). Methods: Ten women with metastatic human epidermal growth factor receptor 2-positive breast cancer underwent 18F-FDG PET/CT and 64Cu-DOTA-trastuzumab PET/CT on days 1 and 2 before treatment with T-DM1. Results: T-DM1-responsive patients had higher uptake than nonresponsive patients. Day 1 minimum SUVmax (5.6 vs. 2.8, P < 0.02), day 2 minimum SUVmax (8.1 vs. 3.2, P < 0.01), and day 2 average SUVmax (8.5 vs. 5.4, P < 0.05) for 64Cu-DOTA-trastuzumab all favored responding patients. Tumor-level response suggested threshold dependence on SUVmax Patients with a day 2 minimum SUVmax above versus below the threshold had a median time to treatment failure of 28 mo versus 2 mo (P < 0.02). Conclusion: Measurement of trastuzumab uptake in tumors via PET/CT is promising for identifying patients with metastatic breast cancer who will benefit from T-DM1.

Site-specific conjugation of monodispersed DOTA-PEGn to a thiolated diabody reveals the effect of increasing peg size on kidney clearance and tumor uptake with improved 64-copper PET imaging.

Optimal PET imaging of tumors with radiolabeled engineered antibodies requires, among other parameters, matching blood clearance and tumor uptake with the half-life of the engineered antibody. Although diabodies have favorable molecular sizes (50 kDa) for rapid blood clearance (t(1/2) = 30-60 min) and are bivalent, thereby increasing tumor uptake, they exhibit substantial kidney uptake as their major route of clearance, which is especially evident when they are labeled with the PET isotope (64)Cu (t(1/2) = 12 h). To overcome this drawback, diabodies may be conjugated to PEG, a modification that increases the apparent molecular size of the diabody and reduces kidney uptake without adversely affecting tumor uptake or the tumor to blood ratio. We show here that site-specific attachment of monodispersed PEGn of increasing molecular size (n = 12, 24, and 48) can uniformly increase the apparent molecular size of the PEG-diabody conjugate, decrease kidney uptake, and increase tumor uptake, the latter due to the increased residence time of the conjugate in the blood. Since the monodispersed PEGs were preconjugated to the chelator DOTA, the conjugates were able to bind radiometals such as (111)In and (64)Cu that can be used for SPECT and PET imaging, respectively. To allow conjugation of the DOTA-PEG to the diabody, the DOTA-PEG incorporated a terminal cysteine conjugated to a vinyl sulfone moiety. In order to control the conjugation chemistry, we have engineered a surface thiolated diabody that incorporates two cysteines per monomer (four per diabody). The thiolated diabody was expressed and purified from bacterial fermentation and only needs to be reduced prior to conjugation to the DOTA-PEGn-Cys-VS. This novel imaging agent (a diabody with DOTA-PEG48-Cys-VS attached to introduced thiols) gave up to 80%ID/g of tumor uptake with a tumor to blood ratio (T/B) of 8 at 24 h when radiolabeled with (111)In and 37.9% ID/g of tumor uptake (T/B = 8) at 44 h when radiolabeled with (64)Cu in PET imaging in an animal model. Tumor uptake was significantly improved from the 50% ID/g at 24 h observed with diabodies that were pegylated on surface lysine residues. Importantly, there was no loss of immunoreactivity of the site-specific Cys-conjugated diabody to its antigen (TAG-72) compared to the parent, unconjugated diabody. We propose that thiolated diabodies conjugated to DOTAylated monodisperse PEGs have the potential for superior SPECT and PET imaging in a clinical setting.

Comparison of CD38-Targeted α- Versus ß-Radionuclide Therapy of Disseminated Multiple Myeloma in an Animal Model.

Targeted therapies for multiple myeloma (MM) include the anti-CD38 antibody daratumumab, which, in addition to its inherent cytotoxicity, can be radiolabeled with tracers for imaging and with ß- and α-emitter radionuclides for radioimmunotherapy. Methods: We have compared the potential therapeutic efficacy of ß- versus α-emitter radioimmunotherapy using radiolabeled DOTA-daratumumab in a preclinical model of disseminated multiple myeloma. Multiple dose levels were investigated to find the dose with the highest efficacy and lowest toxicity. Results: In a dose­response study with the ß-emitter 177Lu-DOTA-daratumumab, the lowest tested dose, 1.85 MBq, extended survival from 37 to 47 d but did not delay tumor growth. Doses of 3.7 and 7.4 MBq extended survival to 55 and 58 d, respectively, causing a small equivalent delay in tumor growth, followed by regrowth. The higher dose, 11.1 MBq, eradicated the tumor but had no effect on survival compared with untreated controls, because of whole-body toxicity. In contrast, the α-emitter 225Ac-DOTA-daratumumab had a dose-dependent effect, in which 0.925, 1.85, and 3.7 kBq increased survival, compared with untreated controls (35 d), to 47, 52, and 73 d, respectively, with a significant delay in tumor growth for all 3 doses. Higher doses of 11.1 and 22.2 kBq resulted in equivalent survival to 82 d but with significant whole-body toxicity. Parallel studies with untargeted 225Ac-DOTA-trastuzumab conferred no improvement over untreated controls and resulted in whole-body toxicity. Conclusion: We conclude, and mathematic modeling confirms, that maximal biologic doses were achieved by targeted α-therapy and demonstrated 225Ac to be superior to 177Lu in delaying tumor growth and decreasing whole-body toxicity.

Preclinical PET Imaging of NTSR-1-Positive Tumors with 64Cu- and 68Ga-DOTA-Neurotensin Analogs and Therapy with an 225Ac-DOTA-Neurotensin Analog.

Background: The aim of the study was to perform PET imaging and radiotherapy with a novel neurotensin derivative for neurotensin receptor 1 (NTSR-1)-positive tumors in an animal model. Materials and Methods: A di-DOTA analog of NT(6-13) with three unnatural amino acids was synthesized and radiolabeled with either 64Cu or 68Ga and tested for serum stability and tumor imaging in mice bearing NTSR-1-positive PC3, and HT29 xenografts. A dose-response therapy study was performed with 18.5, 37, and 74 kBq of 225Ac-di-DOTA-α,ɛ-Lys-NT(6-13). Results: 68Ga-di-DOTA-α,ɛ-Lys-NT(6-13) was >99% stable in serum for 48 h, had an IC50 of 5 nM using 125I labeled NT(8-13) for binding to HT-29 cells, and high uptake in tumor models expressing NTSR-1. 68Ga-di-DOTA-α,ɛ-Lys-NT(6-13) had an average %ID/g (n = 4) at 2 h of 4.0 for tumor, 0.5 for blood, 12.0 for kidney, and <1 for other tissues, resulting in a favorable T/B of 8. Mean survivals of tumor-bearing mice treated with 18.5 or 37 kBq of 225Ac-di-DOTA-α,ɛ-Lys-NT(6-13) were 81 and 93 d, respectively, versus 53 d for controls. Whole-body toxicity was seen for the 74 kBq dose. Conclusions: Based on the results of the animal model, di-DOTA-α,ɛ-Lys-NT(6-13) is a useful imaging agent for NTSR-1-positive tumors when radiolabeled with 68Ga, and when radiolabeled with 225Ac, a potent therapeutic agent.

TAG-72-Targeted α-Radionuclide Therapy of Ovarian Cancer Using 225Ac-Labeled DOTAylated-huCC49 Antibody.

Radioimmunotherapy, an approach using radiolabeled antibodies, has had minimal success in the clinic with several ß-emitting radionuclides for the treatment of ovarian cancer. Alternatively, radioimmunotherapy with α-emitters offers the advantage of depositing much higher energy over shorter distances but was thought to be inappropriate for the treatment of solid tumors, for which antibody penetration is limited to a few cell diameters around the vascular system. However, the deposition of high-energy α-emitters to tumor markers adjacent to a typical leaky tumor vascular system may have large antitumor effects at the tumor vascular level, and their reduced penetration in normal tissue would be expected to lower off-target toxicity. Methods: To evaluate this concept, DOTAylated-huCC49 was labeled with the α-emitter 225Ac to target tumor-associated glycoprotein 72-positive xenografts in a murine model of ovarian cancer. Results:225Ac-labeled DOTAylated-huCC49 radioimmunotherapy significantly reduced tumor growth in a dose-dependent manner (1.85, 3.7, and 7.4 kBq), with the 7.4-kBq dose extending survival by more than 3-fold compared with the untreated control. Additionally, a multitreatment regime (1.85 kBq followed by 5 weekly doses of 0.70 kBq for a total of 5.4 kBq) extended survival almost 3-fold compared with the untreated control group, without significant off-target toxicity. Conclusion: These results establish the potential for antibody-targeted α-radionuclide therapy for ovarian cancer, which may be generalized to α-radioimmunotherapy in other solid tumors.

Anti-CD25 radioimmunotherapy with BEAM autologous hematopoietic cell transplantation conditioning in Hodgkin lymphoma.

High-risk relapsed or refractory (R/R) classical Hodgkin lymphoma (HL) is associated with poor outcomes after conventional salvage therapy and autologous hematopoietic cell transplantation (AHCT). Post-AHCT consolidation with brentuximab vedotin (BV) improves progression-free survival (PFS), but with increasing use of BV early in the treatment course, the utility of consolidation is unclear. CD25 is often expressed on Reed-Sternberg cells and in the tumor microenvironment in HL, and we hypothesized that the addition of 90Y-antiCD25 (aTac) to carmustine, etoposide, cytarabine, melphalan (BEAM) AHCT would be safe and result in a transplantation platform that is agnostic to prior HL-directed therapy. Twenty-five patients with high-risk R/R HL were enrolled in this phase 1 dose-escalation trial of aTac-BEAM. Following an imaging dose of 111In-antiCD25, 2 patients had altered biodistribution, and a third developed an unrelated catheter-associated bacteremia; therefore, 22 patients ultimately received therapeutic 90Y-aTac-BEAM AHCT. No dose-limiting toxicities were observed, and 0.6 mCi/kg was deemed the recommended phase 2 dose, the dose at which the heart wall would not receive >2500 cGy. Toxicities and time to engraftment were similar to those observed with standard AHCT, though 95% of patients developed stomatitis (all grade 1-2 per Bearman toxicity scale). Seven relapses (32%) were observed, most commonly in patients with ≥3 risk factors. The estimated 5-year PFS and overall survival probabilities among 22 evaluable patients were 68% and 95%, respectively, and non-relapse mortality was 0%. aTac-BEAM AHCT was tolerable in patients with high-risk R/R HL, and we are further evaluating the efficacy of this approach in a phase 2 trial. This trial was registered at www.clinicaltrials.gov as #NCT01476839.

Role of theranostics in thoracic oncology.

Theranostics is a re-emerging field of medicine that aims to create targeted agents that can be used for diagnostic and/or therapeutic indications. In the past, theranostics has been used to treat neoplasms, such as thyroid cancer and neuroblastomas. More recently, theranostics has seen a resurgence with advent of new therapeutic antibodies and small molecules which can be transformed into Theranostic agents through radioconjugating with a radioactive isotope. Positron emitting radioisotopes can be used for diagnostic purposes while alpha- and beta-emitting radioisotopes can be used for therapy. The technique of radiolabeling an existing therapeutic agent (small molecule or antibody) leverages the existing qualities of that drug, and potentiates therapeutic effect by conjugating it with a cytotoxic-energy bearing radioisotope (e.g., 131-iodine, 177-lutetium). Theranostics have been used for a few decades now, starting with 131-iodine for therapy of autoimmune thyroiditis (Graves' disease, Hashimoto's thyroiditis) as well as for thyroid cancer. Additionally, 131-iodine-meta-iodobenzylguanidine (131-I-MIBG) initially had been used for gastroenteropancreatic neuroendocrine (carcinoid) tumors. However, recently clinical trials have start enrolling patients to evaluate efficacy of 131-I-MIBG in patients with small cell carcinoma of the lung. In the era of precision medicine and personalized targeted therapeutics, Theranostics can play a key pivotal in improving diagnostic and therapeutic specificity by increasing potency of these targeted small molecules and antibodies with radioisotopes. In this review, we will review various clinically relevant Theranostics agent and their utility in thoracic disorders, notably within oncology.

Improved targeting of an anti-TAG-72 antibody drug conjugate for the treatment of ovarian cancer.

INTRODUCTION: Ovarian cancer has only a 17% 5-year survival rate in patients diagnosed with late stage disease. Tumor-associated glycoprotein-72 (TAG72), expressed in 88% of all stages of ovarian cancer, is an excellent candidate for antibody-targeted therapy, as it is not expressed in normal human adult tissues, except in the secretory endometrium. METHODS: Using the clinically relevant anti-TAG72 murine monoclonal antibody CC49, we evaluated antibody drug conjugates (ADCs) incorporating the highly potent, synthetic antimitotic agent monomethylauristatin E (MMAE). MMAE was conjugated to CC49 via reduced disulfides in the hinge region, using three different types of linker chemistry, vinylsulfone (VS-MMAE), bromoacetamido (Br-MMAE), and maleimido (mal-MMAE). RESULTS: The drug antibody ratios (DARs) of the three ADCs were 2.3 for VS-MMAE, 10 for Br-MMAE, and 9.5 for mal-MMAE. All three ADCs exhibited excellent tumor to blood ratios on PET imaging, but the absolute uptake of CC49-mal-MMAE (3.3%ID/g) was low compared to CC49-Br-MMAE (6.43%ID/g), at 142 hours. Blood clearance at 43 hours was 38% for intact CC49, about 24% for both CC49-VS-MMAE and CC49-Br-MMAE, and 7% for CC49-mal-MMAE. CC49-VS-MMAE was not further studied due to its low DAR, while CC49-mal-MMAE was ineffective in the OVCAR3 xenograft likely due to its rapid blood clearance. In contrast, CC49-Br-MMAE treated mice exhibited an average of a 15.6 day tumor growth delay and a 40% increase in survival vs controls with four doses of 7.5 or 15 mg/kg of CC49-Br-MMAE. CONCLUSION: We conclude that CC49-Br-MMAE with a high DAR and stable linker performs well in a difficult to treat solid tumor model.

Identifying CD38+ cells in patients with multiple myeloma: first-in-human imaging using copper-64-labeled daratumumab.

18F-Fluorodeoxyglucose (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 nonmalignant 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 64Cu via the chelator DOTA (64Cu-daratumumab), led to improved sensitivity and specificity over that of FDG. Here, we report the results of a phase 1 trial designed to (1) assess the safety and feasibility of 64Cu-daratumumab PET/CT and (2) preliminarily evaluate and characterize the ability of 64Cu-daratumumab to accurately detect or exclude MM lesions. A total of 12 daratumumab-naive patients were imaged. Prior to the injection of 15 mCi/5 mg of 64Cu-daratumumab, patients were treated with 0 (n = 3), 10 (n = 3), 45 (n = 3), or 95 mg (n = 3) of unlabeled daratumumab to assess its effect on image quality. No significant adverse events were observed from either unlabeled daratumumab or 64Cu-daratumumab. Of the dose levels tested, 45 mg unlabeled daratumumab was the most optimal in terms of removing background signal without saturating target sites. 64Cu-daratumumab PET/CT provided safe whole-body imaging of MM. A trial comparing the sensitivity and specificity of 64Cu-daratumumab PET/CT with that of FDG PET/CT is planned. This trial was registered at www.clinicaltrials.gov as #NCT03311828.