Intraperitoneal Injection is Not Always a Suitable Alternative to Intravenous Injection for Radiotherapy

Abstract Intraperitoneal (IP) injection is frequently reported to be as effective as intravenous (IV) injection. Because it allows administering a larger volume with more radioactivity, we have investigated this route and the possibility of using it to circumvent the volume constraint we earlier experienced with pretargeting radiotherapy. Using 99mTc as the label, the pharmacokinetics (PK) of the cMORF effector (a DNA analogue) was evaluated after IP or IV injection in normal mice by necropsy and SPECT/CT imaging. In another experiment, nude mice bearing tumors were used and they received MORF-CC49 pretargeting antibody IV 2 days earlier than labeled cMORF IV or IP. Tumor accumulations of cMORF were measured at 6 hours after its injections. The absorbed radiation doses for 188Re or 90Y pretargeting were estimated using the 99mTc data and a self-absorbed model. Although the absorbed radiation doses to other organs were comparable, the dose to intestines after IP injection was 30-fold higher than IV injection due to the slow entry into the circulation. It had reached such a level as high as the dose to the kidneys that cleared the radioactivity and usually were at the highest level. Nevertheless, the slow entry did not reduce the tumor accumulation. In conclusion, using IP in place of IV led to an unacceptably high absorbed radiation dose to the intestines although the tumor accumulation was not compromised. This effect may be applicable to other radiotherapeutic agents as well

Differentiation between temporary and real non-clearability of biotinylated IgG antibody by avidin in mice

Although an increasing number of antibody conjugates are being used in the clinic, there remain many unmet needs in antibody targeting. Normal tissue background is one of the key issues that limits the therapeutic efficacy and the detection sensitivity. Background reduction coupled with dose increase may provide the required target accumulation of the label or toxin at an acceptable normal tissue background. However, the knowledge about the in vivo interaction between antibody and a clearing agent is currently inadequate for designing a rational clearance regimen or system. The current investigation focuses on the clearability of antibody for background reduction, an important topic to antibody targeting in general. The investigation employs pretargeting as a research tool and avidin as a model clearing agent. By comparing the effects of natural clearance at a longer post-injection time and avidin clearance, we demonstrated that avidin clearance is much more effective. By directly attaching avidin to a biotinylated antibody prior to injection, we found that the biotinylated antibody in blood, once bound to the clearing agent, can be removed from the circulation immediately and completely, while the real non-clearable antibody without biotin stays. The study of multiple avidin injections confirmed that the presence of clearable biotinylated antibodies after an avidin injection is due to their temporary inaccessibility and subsequent return from tissue compartments. The collective clearance efficiency of 91% by three avidin injections indicates a continuous IV infusion would be recommended to remove all of the biotinylated IgG molecules. In conclusion, the use of antibody pretargeting as a tool in this study has improved understanding of the incomplete clearance by avidin and can aid in overcoming this obstacle

Targeted scVEGF/(177)Lu radiopharmaceutical inhibits growth of metastases and can be effectively combined with chemotherapy

BACKGROUND: scVEGF/(177)Lu is a novel radiopharmaceutical targeted by recombinant single-chain (sc) derivative of vascular endothelial growth factor (VEGF) that binds to and is internalized by vascular endothelial growth factor receptors (VEGFR). scVEGF/(177)Lu potential as adjuvant and neoadjuvant anti-angiogenic therapy was assessed in metastatic and orthotopic mouse models of triple-negative breast cancer. METHODS: Metastatic lesions in Balb/c mice were established by intracardiac injection of luciferase-expressing 4T1luc mouse breast carcinoma cells. Mice with metastatic lesions received single intravenous (i.v.) injection of well-tolerated dose of scVEGF/(177)Lu (7.4 MBq/mouse) at day 8 after 4T1luc cell injection. Primary orthotopic breast tumors in immunodeficient mice were established by injecting luciferase-expressing MDA231luc human breast carcinoma cells into mammary fat pad. Tumor-bearing mice were treated with single injections of scVEGF/(177)Lu (7.4 MBq/mouse, i.v), or liposomal doxorubicin (Doxil, 1 mg doxorubicin per kg, i.v.), or with a combination of Doxil and scVEGF/(177)Lu given at the same doses, but two hours apart. Cold scVEGF-targeting conjugate was included in controls and in Doxil alone group. The effects of treatments were defined by bioluminescent imaging (BLI), computed tomography (CT), computed microtomography (microCT), measurements of primary tumor growth, and immunohistochemical analysis. RESULTS: In metastatic model, adjuvant treatment with scVEGF/(177)Lu decreased overall metastatic burden and improved survival. In orthotopic primary tumor model, a combination of Doxil and scVEGF/(177)Lu was more efficient in tumor growth inhibition than each treatment alone. scVEGF/(177)Lu treatment decreased immunostaining for VEGFR-1, VEGFR-2, and pro-tumorigenic M2-type macrophage marker CD206. CONCLUSIONS: Selective targeting of VEGFR with well-tolerated doses of scVEGF/(177)Lu is effective in metastatic and primary breast cancer models and can be combined with chemotherapy. As high level of VEGFR expression is a common feature in a variety of cancers, targeted delivery of (177)Lu for specific receptor-mediated uptake warrants further exploration

Pharmacokinetics in patients of an anti-carcinoembryonic antigen antibody radiolabeled with indium-111 using a novel diethylenetriamine pentaacetic acid chelator

The pharmacokinetics of the C110 anti-carcinoembryonic antigen antibody radiolabeled with 111In via a novel benzylisothiocyanate derivative of diethylenetriamine pentaacetic acid have been determined in 12 patients. The chelator was attached to the protein via a thiourea bond and in such a way that all 5 carboxymethyl arms were presumably able to participate in chelation. Patients with known or suspected colorectal carcinoma received between 5 and 20 mg of the IgG antibody labeled with 5 mCi of 111In. Individual organ radioactivity levels were quantitated, and serum and urine samples were analyzed, principally by size exclusion high-performance liquid chromatography (HPLC). Total urinary excretion averaged 0.18% of the injected dose/h with large patient to patient variation. At early times postadministration (less than 8 h) the predominant radiolabeled species in urine was free diethylenetriamine pentaacetic acid most probably administered as a small radiocontaminant in the injectate. Thereafter, radioactivity in urine was primarily present as a low molecular weight catabolic product. Analysis of serum by size exclusion HPLC occasionally showed 3 radioactivity peaks, 2 of which are due to circulating immune complexes and labeled antibody. The third peak is of low molecular weight and is due to one or more products of antibody catabolism. Transchelation of 111In to circulating transferrin was observed but at modest levels. Quantitation of organ radioactivity showed that 18 +/- 4 (SD)% of the injected dose was in the liver at 1 day postadministration and 1.4 +/- 1.1 and 1.2 +/- 0.9% was in the spleen and in both kidneys, respectively, at this time. The mean half-life for clearance of total injected radioactivity was fitted to a single exponential and was found to be 34 h (SD, 14 h; N = 13) and that for antibody alone, assessed by size exclusion HPLC analysis of serum samples, was calculated to be 22 h (SD, 8 h; N = 10). Neither of these values nor organ radioactivity levels were affected by antibody-loading dose

Pharmacokinetics of 111In-labeled OC-125 antibody in cancer patients compared with the 19-9 antibody

We recently reported on the pharmacokinetics in 14 cancer patients of the 19-9 antibody radiolabeled with 111In. We have now repeated this investigation in 18 cancer patients using the OC-125 antibody, in part to compare the in vivo behavior of two murine monoclonal antibodies of the same subclass administered as the F(ab\u27)2 fragments, by the same route and at the same dose. As in the earlier investigation, 1 mg of fragments was infused i.v., and organ quantitation was obtained for up to 72 h along with frequent blood and urine samples for chromatographic evaluation. Analysis of urine showed that activity clearance by this route amounted to 0.29%/h and consisted of labeled DTPA only in early samples and metabolic products thereafter. Analysis of serum samples often showed the presence of a high-molecular-weight species appearing within 24 h. This species is probably due to antibody binding to circulating antigen, although the percentage of circulating activity present as this species did not correlate well with circulating antigen levels. As before, organ accumulation was greatest in the liver, although levels were significantly reduced (12% compared to 20% of administered dose at 24 h, P less than 0.01). Plasma clearance was also significantly different: whereas the label in the case of the OC-125 antibody showed one-compartment clearance kinetics and remained in the plasma compartment, in the 19-9 case the label diffused to a second, unidentified compartment

Activin–like kinase–3 activity is important for kidney regeneration and reversal of fibrosis

Molecules associated with TGF-β superfamily such as BMPs and TGF-β are key regulators of inflammation, apoptosis and cellular transitions. Here, we demonstrate that the BMP receptor activin–like kinase 3 (Alk3) is elevated early in response to kidney injury and its deletion in the tubular epithelium leads to enhanced TGF-β1 / Smad3 signaling, epithelial damage and fibrosis, suggesting a protective role for Alk3 mediated signaling. Structure–function analysis of Alk3 / BMP / BMPRII ligand–receptor complex coupled with synthetic organic chemistry led us to construct a library of small peptide agonists of BMP signaling that function via Alk3 receptor. One such peptide agonist, THR–123, suppressed inflammation, apoptosis epithelial–to–mesenchymal transition program, and reversed fibrosis in mouse models of acute and chronic injury. Combining THR–123 and angiotensin–converting enzyme inhibitor, captopril, exhibited additive therapeutic benefit in controlling fibrosis. Our studies demonstrate that BMP signaling agonists constitute a new line of therapeutic agents with a potential utility in the clinic to induce regeneration, repair and reverse fibrosis

Imaging Net Retrograde Axonal Transport In Vivo: A Physiological Biomarker

OBJECTIVE: The objective of this study is to develop a novel method for monitoring the integrity of motor neurons in vivo by quantifying net retrograde axonal transport. METHODS: The method uses single photon emission computed tomography to quantify retrograde transport to spinal cord of tetanus toxin fragment C ((125) I-TTC) following intramuscular injection. We characterized the transport profiles in 3 transgenic mouse models carrying amyotrophic lateral sclerosis (ALS)-associated genes, aging mice, and SOD1(G93A) transgenic mice following CRISPR/Cas9 gene editing. Lastly, we studied the effect of prior immunization of tetanus toxoid on the transport profile of TTC. RESULTS: This technique defines a quantitative profile of net retrograde axonal transport of TTC in living mice. The profile is distinctly abnormal in transgenic SOD1(G93A) mice as young as 65 days (presymptomatic) and worsens with disease progression. Moreover, this method detects a distinct therapeutic benefit of gene editing in transgenic SOD1(G93A) mice well before other clinical parameters (eg, grip strength) show improvement. Symptomatic transgenic PFN1(C71G/C71G) ALS mice display gross reductions in net retrograde axonal transport, which is also disturbed in asymptomatic mice harboring a human C9ORF72 transgene with an expanded GGGGCC repeat motif. In wild-type mice, net retrograde axonal transport declines with aging. Lastly, prior immunization with tetanus toxoid does not preclude use of this assay. INTERPRETATION: This assay of net retrograde axonal transport has broad potential clinical applications and should be particularly valuable as a physiological biomarker that permits early detection of benefit from potential therapies for motor neuron diseases