Zhengsheng Yao

Interleukin-15 combined with an anti-CD40 antibody provides enhanced therapeutic efficacy for murine models of colon cancer

IL-15 has potential as an immunotherapeutic agent for cancer treatment because it is a critical factor for the proliferation and activation of natural killer (NK) and CD8+ T cells. Administration of anti-CD40 antibodies has shown anti-tumor effects in vivo through a variety of mechanisms. Furthermore, activation of CD40 led to increased expression of IL-15 receptor-α by dendritic cells, an action that is critical for trans-presentation of IL-15 to NK and CD8+ T cells. In this study, we investigated the therapeutic efficacy of the combination regimen of murine IL-15 (mIL-15) with an agonistic anti-CD40 antibody (FGK4.5) in murine lung metastasis models involving CT26 and MC38, which are murine colon cancer cell lines syngeneic to BALB/c and C57BL/6 mice, respectively. Treatment with mIL-15 or the anti-CD40 antibody alone significantly prolonged survival of both CT26 and MC38 tumor-bearing mice compared with the mice in the PBS solution control group (P < 0.01). Furthermore, combination therapy with both mIL-15 and the anti-CD40 antibody provided greater therapeutic efficacy as demonstrated by prolonged survival of the mice compared with either mIL-15 or the anti-CD40 antibody-alone groups (P < 0.001). We found that NK cells isolated from the mice that received the combination regimen expressed increased levels of intracellular granzyme B and showed stronger cytotoxic activity on the target cells. The findings from this study provide the scientific basis for clinical trials using the combination regimen of IL-15 with an anti-CD40 antibody for the treatment of patients with cancer.

Diagnostic value of Tc-99m (V) DMSA for chondrogenic tumors with positive Tc-99m HMDP uptake on bone scintigraphy

Technetium-99m (V) DMSA scintigraphy was performed In 17 patients with 37 chondrogenic tumors (13 osteochondromas, 14 enchondromas, and 10 chondrosarcomas) that had previously shown uptake of Tc-99m HMDP. Technetium-99m (V) DMSA showed high uptake by all chondrosarcomas, but low or no uptake always indicated benign chondrogenic tumors. Technetium-99m (V) DMSA scintigraphy may be superior to Tc-99m HMDP scintigraphy for distinguishing benign and malignant chondrogenic tumors, and could also be useful for diagnosing the malignant transformation of chondrogenic tumors.

The Anti-CD25 Monoclonal Antibody 7G7/B6, Armed with the α-Emitter 211At, Provides Effective Radioimmunotherapy for a Murine Model of Leukemia

Radioimmunotherapy of cancer with radiolabeled antibodies has shown promise. alpha-Particles are very attractive for cancer therapy, especially for isolated malignant cells, as is observed in leukemia, because of their high linear energy transfer and short effective path length. We evaluated an anti-CD25 [interleukin-2 receptor alpha (IL-2R alpha)] monoclonal antibody, 7G7/B6, armed with (211)At as a potential radioimmunotherapeutic agent for CD25-expressing leukemias and lymphomas. Therapeutic studies were done in severe combined immunodeficient/nonobese diabetic mice bearing the karpas299 leukemia and in nude mice bearing the SUDHL-1 lymphoma. The results from a pharmacokinetic study showed that the clearance of (211)At-7G7/B6 from the circulation was virtually identical to (125)I-7G7/B6. The biodistributions of (211)At-7G7/B6 and (125)I-7G7/B6 were also similar with the exception of a higher stomach uptake of radioactivity with (211)At-7G7/B6. Therapy using 15 microCi of (211)At-7G7/B6 prolonged survival of the karpas299 leukemia-bearing mice significantly when compared with untreated mice and mice treated with (211)At-11F11, a radiolabeled nonspecific control antibody (P < 0.01). All of the mice in the control and (211)At-11F11 groups died by day 46 whereas >70% of the mice in the (211)At-7G7/B6 group still survived at that time. In summary, (211)At-7G7/B6 could serve as an effective therapeutic agent for patients with CD25-expressing leukemias.

Pretargeted α Emitting Radioimmunotherapy Using 213Bi 1,4,7,10-Tetraazacyclododecane-N,N′,N″,N‴-Tetraacetic Acid-Biotin

Purpose: The use of an α emitter for radioimmunotherapy has potential advantages compared with β emitters. When administered systemically optimal targeting of intact antibodies requires >24 h, therefore limiting the use of short-lived α emitters. This study investigated the biodistribution of bismuth-labeled biotin in A431 tumor-bearing mice pretargeted with antibody B3-streptavidin (B3-SA) and examined the therapeutic efficacy of the α emitter, 213Bi-labeled biotin. Experimental Design: Biotinidase-resistant 7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid (DOTA)-biotin was radiolabeled with 205,206Bi or 213Bi. Treatment of tumor-bearing mice began by administration of B3-SA (400 μg) to target the tumor sites for 24 h. Then, an agent containing biotin and galactose groups was used to clear the conjugate from the circulation. Four h later, bismuth-radiolabeled DOTA-biotin was given, and biodistribution or therapy was evaluated. Dose escalation treatment from 3.7–74 MBq was performed, and the effects on tumors of different sizes were investigated. Tumor growth, complete blood cell counts, toxicity, and survival were monitored. Results: Radiolabeled biotin cleared rapidly. Rapid tumor uptake resulted in much higher tumor:nontumor targeting ratios than achieved with the directly labeled monoclonal antibody. Dose escalation revealed that 74 MBq caused acute death of mice, whereas 0.37–37 MBq doses inhibited tumor growth and prolonged survival significantly. Evidence of mild hematological toxicity was noted. At therapeutically effective doses renal toxicity was observed. Conclusions:213Bi-DOTA-biotin, directed by the Pretarget method to tumor-targeted B3-SA, showed a therapeutic effect, although the therapeutic index was low. The source of the toxicity was most likely related to the renal toxicity.

Preparation and in vivo evaluation of linkers for 211At labeling of humanized anti-Tac

The syntheses, radiolabeling, antibody conjugation, and in vivo evaluation of new linkers for 211At labeling of humanized anti-Tac (Hu-anti-Tac), an antibody to the alpha-chain of the IL-2 receptor (IL-2Ralpha) shown to be a useful target for radioimmunotherapy are described. Synthesis of the organometallic linker precursors is accomplished by reaction of the corresponding bromo- or iodoaryl esters with bis(tributyltin) in the presence of a palladium catalyst. Subsequent conversion to the corresponding N-succinimidyl ester and labeling with 211At of two new linkers, N-succinimidyl 4-[211At]astato-3-methylbenzoate and N-succinimidyl N-(4-[211At]astatophenethyl)succinamate (SAPS), together with the previously reported N-succinimidyl 4-[211At]astatobenzoate and N-succinimidyl 3-[211At]astato-4-methylbenzoate, are each conjugated to Hu-anti-Tac. The plasma survival times of these conjugates are compared to those of directly iodinated (125I) Hu-anti-Tac. The N-succinimidyl N-(4-[211At]astatophenethyl)succinamate compound (SAPS) emerged from this assay as the most viable candidate for 211At-labeling of Hu-anti-Tac. SAPS, along with the directly analogous radio-iodinated reagent, N-succinimidyl N-(4-[125I]astatophenethyl)succinamate (SIPS), are evaluated in a biodistribution study along with directly iodinated (125I) Hu-anti-Tac. Blood clearance and biological accretion results indicate that SAPS is a viable candidate for further evaluation for radioimmunotherapy of cancer.

Effective therapy of murine models of human leukemia and lymphoma with radiolabeled anti-CD30 antibody, HeFi-1.

CD30 is a member of the TNF receptor superfamily. Overexpression of CD30 on some neoplasms versus limited expression on normal tissues makes this receptor a promising target for antibody-based therapy. Radioimmunotherapy of cancer with radiolabeled antibodies has shown promise. In this study, we evaluated the therapeutic efficacy of an anti-CD30 antibody, HeFi-1, armed with 211At in a leukemia (karpas299) model and with 90Y in a lymphoma (SUDHL-1) model. Furthermore, we investigated the combination therapy of 211At-HeFi-1 with unmodified HeFi-1 in the leukemia model. Treatment with unmodified HeFi-1 significantly prolonged the survival of the karpas299-bearing mice compared with the controls (P < 0.001). Treatment with 211At-HeFi-1 showed greater therapeutic efficacy than that with unmodified HeFi-1 as shown by survival of the mice (P < 0.001). Combining these two agents further improved the survival of the mice compared with the groups treated with either 211At-HeFi-1 (P < 0.05) or unmodified HeFi-1 (P < 0.001) alone. In the lymphoma model, the survival of the SUDHL-1-bearing mice was significantly prolonged by the treatment with 90Y-HeFi-1 compared with the controls (P < 0.001). In summary, radiolabeled HeFi-1 is very promising for the treatment of CD30-expressing leukemias and lymphomas, and the combination regimen of 211At-HeFi-1 with unmodified HeFi-1 enhanced the therapeutic efficacy.

Comparison of the Chase Effects of Avidin, Streptavidin, Neutravidin, and Avidin‐Ferritin on a Radiolabeled Biotinylated Anti‐tumor Monoclonal Antibody

Injection of avidin can decrease the background radioactivity due to a radiolabeled biotinylated monoclonal antibody. We compared the chase effects of avidin, streptavidin, neutravidin, and avidin‐conjugated ferritin on a radiolabeled antitumor monoclonal antibody in tumor‐bearing nude mice. A radioiodine‐labeled biotinylated monoclonal antibody (OST7) was administered to athymic mice bearing osteogenic sarcomas. After 24 h, an avidin, streptavidin, neutravidin or avidin‐conjugated ferritin chaser was intravenously injected into the mice. At 2 h after the chase, the biodistribution of the radiolabeled monoclonal antibody was determined. Clearance from the blood was dose‐dependently accelerated by avidin and its effect was 10‐fold stronger than that of neutravidin or avidinferritin. Streptavidin did not promote clearance of the biotinylated antibody. Avidin was the most effective chasing agent for improving the biodistribution of the radiolabeled biotinylated monoclonal antibody among the four avidin derivatives tested.

Intravenous avidin chase improved localization of radiolabeled streptavidin in intraperitoneal xenograft pretargeted with biotinylated antibody

In the present study, we examined the effect of avidin administered intravenously (i.v.) on the biodistribution of radiolabeled streptavidin in mice bearing intraperitoneal (IP) xenografts pretargeted with biotinylated antibody. Tumors were established in nude mice by IP inoculation of LS180 human colon cancer cells. Monoclonal antibody MLS128, which recognizes Tn antigen on mucin, was biotinylated and injected IP into the IP tumor-bearing mice. Radioiodinated streptavidin was administered IP or i.v. 48 h after pretargeting of biotinylated antibody. Avidin was administered i.v. 30 min prior to streptavidin injection. The localization of radioiodinated streptavidin in the tumor pretargeted with biotinylated antibody was significantly higher than that without pretargeting and that of radioiodinated MLS128 by the one-step method. Avidin administration significantly accelerated the clearance of radioiodinated streptavidin in blood and other normal tissues and increased the tumor-to-blood radioactivity ratio regardless of administration route of streptavidin. The i.v. avidin chase improved tumor localization of radiolabeled streptavidin in the IP xenografts pretargeted with biotinylated antibody.

Augmented IL-15Rα Expression by CD40 Activation Is Critical in Synergistic CD8 T Cell-Mediated Antitumor Activity of Anti-CD40 Antibody with IL-15 in TRAMP-C2 Tumors in Mice

IL-15 has potential as an immunotherapeutic agent for cancer treatment because it is a critical factor for the proliferation and activation of NK and CD8+ T cells. However, monotherapy of patients with malignancy with IL-15 that has been initiated may not be optimal, because of the limited expression of the private receptor, IL-15Rα. We demonstrated greater CD8 T cell-mediated therapeutic efficacy using a combination regimen of murine IL-15 administered with an agonistic anti-CD40 Ab (FGK4.5) that led to increased IL-15Rα expression on dendritic cells (DCs), as well as other cell types, in a syngeneic established TRAMP-C2 tumor model. Seventy to one hundred percent of TRAMP-C2 tumor-bearing wild-type C57BL/6 mice in the combination group manifested sustained remissions, whereas only 0–30% in the anti-CD40–alone group and none in the murine IL-15–alone group became tumor free (p < 0.001). However, the combination regimen showed less efficacy in TRAMP-C2 tumor-bearing IL-15Rα−/− mice than in wild-type mice. The combination regimen significantly increased the numbers of TRAMP-C2 tumor-specific SPAS-1/SNC9-H8 tetramer+CD8+ T cells, which were associated with the protection from tumor development on rechallenge with TRAMP-C2 tumor cells. Using an in vitro cytolytic assay that involved NK cells primed by wild-type or IL-15Rα−/− bone marrow-derived DCs, we demonstrated that the expression of IL-15Rα by DCs appeared to be required for optimal IL-15–induced NK priming and killing. These findings support the view that anti-CD40–mediated augmented IL-15Rα expression was critical in IL-15–associated sustained remissions observed in TRAMP-C2 tumor-bearing mice receiving combination therapy.

Effect of chelator conjugation level and injection dose on tumor and organ uptake of 111In-labeled MORAb-009, an anti-mesothelin antibody.

INTRODUCTION Radiolabeling of a monoclonal antibody (mAb) with a metallic radionuclide requires the conjugation of a bifunctional chelator to the mAb. The conjugation, however, can alter the physical and immunological properties of the mAb, consequently affecting its tumor-targeting pharmacokinetics. In this study, we investigated the effect of the amount of 2-(p-isothiocyanatobenzyl)-cyclohexyl-diethylenetriamine-pentaacetic acid (CHX-A″) conjugated to MORAb-009, a mAb directed against mesothelin, and the effect of MORAb dose on the biodistribution of (111)In-labeled MORAb-009. METHODS We used nude mice bearing the A431/K5 tumor as a mesothelin-positive tumor model and the A431 tumor as a mesothelin-negative control. To find the optimal level of CHX-A″ conjugation, CHX-A″-MORAb-009 conjugates with 2.4, 3.5 and 5.5 CHX-A″ molecules were investigated. To investigate the effect of injected MORAb-009 dose on neutralizing the shed mesothelin in the circulation, biodistribution studies were performed after the intravenous co-injection of (111)In-labeled MORAb-009 (2.4 CHX-A″/MORAb-009) with three different doses: 0.2, 2 and 30 μg of MORAb-009. RESULTS The tumor uptake in A431/K5 tumor was four times higher than that in A431 tumor, indicating that the tumor uptake in A431/K5 was mesothelin mediated. The conjugate with 5.5 CHX-A″ showed a lower isoelectric point (pI) and lower immunoreactivity (IR) than the 2.4 CHX-A″ conjugate. These differences were reflected in the biodistribution of the (111)In label. The (111)In-labeled MORAb-009 conjugated with 2.4 CHX-A″ produced higher tumor uptake and lower liver and spleen uptakes than the 5.5 CHX-A″ conjugate. The biodistribution studies also revealed that the tumor uptake was significantly affected by the injected MORAb-009 dose and tumor size. The 30-μg dose produced higher tumor uptake than the 0.2- and 2-μg doses, whereas the 30-μg dose produced lower liver and spleen uptakes than the 0.2-μg dose. CONCLUSION This study demonstrates that the number of chelate conjugation and the injected dose are two important parameters to achieve high tumor and low non-target organ uptake of (111)In-labeled MORAb-009. This study also suggests that the injected dose of mAb could be individualized based on the tumor size or the blood level of shed antigen in a patient to achieve the ideal tumor-to-organ radioactivity ratios.