Improved Tumor Radiotherapy by MORF pretargeting

尽管经过几十年的努力，造血系统肿瘤，特别是实体瘤的常规放射免疫治疗仍然提供边际结果。 因此，需要治疗这些疾病的替代方法。 可以说，最有吸引力的替代方法之一涉及预先瞄准。预靶向的临床前研究已经清楚地证明了疗效，早期临床试验正在提供令人鼓舞的结果。 这些研究通常涉及生物素和（链霉菌）抗生物素蛋白。 不幸的是，已发现（链霉菌）抗生物素蛋白具有免疫原性，内源性生物素已显示出干扰作用。另一种涉及双特异性抗体的方法用抗体和半抗原制备中的困难代替这些困难。 双特异性抗体还显示出数量级较低的亲和力-这是预靶向的重要考虑因素。UMMS的研究人员一直在探索99 mTc标记的寡核苷酸，一种DNA化学类似物：肽核酸（PNA），最近，另一种DNA化学类似物：morpholinos（MORF）用于此应用，并在初步研究中表明，用MORF预靶向可能会解决上述困难。 我们已经通过表面等离子体共振表明，18-mer MORF与其MORF互补物（cMORF）的结合速率常数与相当长度的DNA的结合速率常数相等，因此与生物素与（链霉）抗生物素蛋白的结合速率常数相等。 我们还发现，放射性标记的MORF在小鼠中几乎完全通过肾脏显示快速清除动力学。 此外，当然不存在内生的MORF问题。 在给予MN-14-cMORF后，将99 mTc-MAG 3-MORF给予荷LS 174 T肿瘤的裸鼠已经获得了极好的结果。 本研究旨在建立99 mTc在荷瘤小鼠体内预靶向定位的最佳剂量和时间条件。 然后，这些条件将使用188 Re标记的MORF再现，以再次在肿瘤小鼠中研究这种方法的治疗潜力。 这项合作研究汇集了来自Gene Tools的研究人员及其对MORF的了解，来自Immunomedics和Garden State Cancer Center的研究人员及其在治疗预靶向方面的专业知识，以及来自UMMS的研究人员，他们在MORF和其他寡聚体的放射性标记和体内使用方面具有经验。 我们相信，这些研究将证实，与MORF的预靶向治疗可以显着提高后，现在可以实现与传统的放射免疫治疗，并可能是上级预靶向方法涉及生物素/（链霉）亲和素或双特异性抗体。

Despite several decades of effort, conventional radioimmunotherapy of hematopoietic and especially solid tumors is still providing marginal results. As such, alternative methods of treating these diseases are needed. Arguably one of the most attractive alternative approaches involves pretargeting. Preclinical studies of pretargeting have clearly demonstrated efficacy and early clinical trials are providing encouraging results. These studies usually involve biotin and (strept)avidin. Unfortunately (strept)avidin has been found to be immunogenic and endogenous biotin has been shown to interfere. Another approach, involving bispecific antibodies, replace these difficulties with difficulties in antibody and hapten preparation. Bispecific antibodies also show orders-of-magnitude lower affinities - an important consideration for pretargeting. Investigators at UMMS have been exploring 99mTc-labeled oligonucleotides, one DNA chemical analogue: peptide nucleic acid (PNA) and, most recently, another DNA chemical analogue: morpholinos (MORF) for this application and have shown in preliminary studies that pretargeting with MORFs may potentially solve the above difficulties. We have shown by surface plasmon resonance that the association rate constant of a 18-mer MORF for its MORF complement (cMORF) is equivalent of that of DNAs of comparable lengths and therefor equivalent to that of biotin for (strept)avidin. We have also found that radiolabeled MORFs show rapid clearance kinetics in mice almost exclusively through the kidneys. Furthermore, there is, of course, no endogenous MORF problem. Excellent results have already been obtained with 99mTc-MAG3-MORF administered to LS174T tumor bearing nude mice following the administration of MN-14-cMORF. This study will establish the optimum conditions of dosage and timing for pretargeted localization of 99mTc in tumored mice. These conditions will then be reproduced using MORF labeled with 188Re to investigate the therapeutic potential of this approach, again in tumored mice. This collaborative investigation brings together researchers from Gene Tools and their knowledge of MORF, from Immunomedics and Garden State Cancer Center with their expertise in therapeutic pretargeting and from UMMS who have experience in the radiolabeling and in vivo uses of MORFs and other oligomers. We are confident that these investigations will confirm that pretargeting with MORF can significantly improve upon the therapy now achievable with conventional radioimmunotherapy and may be superior to pretargeting approaches involving biotin/(strept)avidin or bifspecific antibodies.