Improved Tumor Radiotherapy by MORF pretargeting

尽管几十年的努力，传统的放射免疫治疗的造血，特别是实体瘤仍然提供边际效果。因此，需要治疗这些疾病的替代方法。可以说，最具吸引力的替代方法之一是预先定位。临床前研究已经清楚地证明了预靶向的有效性，早期临床试验也提供了令人鼓舞的结果。这些研究通常涉及生物素和（链球菌）亲和素。不幸的是，（链球菌）亲和素已被发现具有免疫原性，内源性生物素已被证明有干扰作用。另一种方法，涉及双特异性抗体，用抗体和半抗原制备的困难取代了这些困难。双特异性抗体也显示出数量级较低的亲和力-这是预先靶向的重要考虑因素。UMMS的研究人员一直在探索99mtc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）用于该应用，并在初步研究中表明，MORF的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，一个18聚合体的MORF与其MORF补体（cMORF）的结合速率常数相当于相当长度的dna，因此相当于生物素与（strept）亲和素的结合速率常数。我们还发现放射标记的morf在小鼠中几乎完全通过肾脏显示出快速清除动力学。此外，当然不存在内源性MORF问题。在给药MN-14-cMORF之后，给药99mTc-MAG3-MORF给LS174T荷瘤裸鼠已经获得了很好的效果。本研究旨在建立99mTc在肿瘤小鼠体内预靶向定位的最佳剂量和时间条件。然后，这些条件将使用带有188Re标记的MORF重现，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的研究人员和他们在MORF方面的知识，来自免疫医学和Garden State癌症中心的研究人员和他们在治疗预靶向方面的专业知识，以及来自UMMS的研究人员，他们在放射性标记和MORF和其他低聚物的体内使用方面有经验。我们相信，这些研究将证实，MORF的预靶向可以显著改善传统放射免疫疗法的治疗效果，并且可能优于生物素/（链球菌）亲和素或双特异性抗体的预靶向方法。

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.