Development/Bifunctional MR Agents/Diagnosis and Therapy

描述(由申请人提供)： 在我们的初步研究中，将一种有效的光敏剂HPPH(一种叶绿素-a衍生物)与显像剂Gd(11)-氨基苯基DTPA偶联。体内反射光谱证实HPPH-氨基苯基DTPA Gd(III)结合物在C3H小鼠放射性纤维肉瘤(RIF)肿瘤中的摄取高于HPPH单独的摄取。Ward结肠癌大鼠皮下移植瘤静脉注射结肠癌24小时后，MRI信号明显增强。在体外(RIF Tum6r细胞)和体内(携带RIF肿瘤的小鼠)，该结合物都产生了显着的疗效。我们还合成了一种“更高的有效载荷”分子[每个HPPH分子有两个Gd(III)原子]，它也保持了肿瘤亲和性，PDT活性，并且与相关的单Gd(Ill)类似物相比，具有更好的MRI增强能力。不幸的是，在核磁共振剂量(10毫摩尔/公斤)，这些结合物产生严重的皮肤光毒性。然而，用聚乙二醇组取代焦脱镁叶绿酸-a的己基，在注射后8小时产生显著的肿瘤增强，显著的杀瘤活性(90d时80%的小鼠无瘤)，皮肤光毒性比相关的己基醚类似物低。这些结合物的水溶性差的问题通过脂质体制剂得到了解决。 在此，我们建议制备这些细菌氯类似物的Gd(III)DTP结合物，这些细菌氯类似物在750-800 nm附近表现出长波吸收(用于治疗较大的肿瘤)，并且在肿瘤亲和性方面优于HPPH。这些结合物的比较研究将包括：体内反射光谱的肿瘤摄取，体外和体内PDT效率，体内MRI的肿瘤增强(成像)，MR成像剂量下的皮肤光毒性，T1，T2松弛，细胞内定位，以及一般毒理学。最后，我们将通过使用最有效候选物的C-14标记类似物来定义最有效偶联物的生物分布。 开发一种用于核磁共振成像的肿瘤亲和性造影剂本身就代表着癌症诊断的重要一步，但双功能造影剂提供了在诊断性身体扫描之后进行靶向光动力疗法的可能性，将两种方式结合成一种经济高效的“看和治疗”方法。

DESCRIPTION (provided by applicant): In our initial study, an effective photosensitizer, HPPH (a chlorophyll-a derivative) was conjugated with Gd (lll)-aminophenylDTPA, an imaging agent. In vivo reflectance spectroscopy confirmed that tumor uptake of the HPPH-aminophenylDTPA Gd (III)conjugate was higher than that of HPPH alone in the radiation-induced fibrosarcoma (RIF) tumor of C3H mice. The subcutaneously implanted Ward colon carcinoma in rats showed markedly increased MRI signal at twenty-four hours after intravenous injection of the conjugate. Both in vitro (RIF tum6r cells) and in vivo (mice bearing RIF tumors) the conjugate produced significant efficacy. We have also synthesized a "higher payload" molecule [two Gd (III)atoms per HPPH molecule] that also remained tumor-avid, PDT-active, and with improved MRI enhancing ability than the related mono-Gd (Ill) analog. Unfortunately, at the MRI dose (10 mmole/kg), these conjugates produced severe skin phototoxicity. However, replacing the hexyl- group of the pyropheophorbide-a with a PEG group, produced remarkable tumor enhancing at 8 hour postinjection, significant tumoricidal activity (80% of mice were tumor free on day 90) with reduced skin phototoxicity than the related hexyl- ether analogs. The poor water-solubility problem of these conjugates was resolved by liposomal formulation. We herein propose to prepare the Gd (III)DTP conjugate of those bacteriochlorin analogs that exhibit long wavelength absorption near 750-800 nm (for treating larger tumors) and are superior in terms of tumoravidity than HPPH. The comparative study of the conjugates wilt include: tumor uptake by in vivo reflectance spectroscopy, in vitro and in vivo PDT efficacy, tumor enhancement (imaging) by in vivo MRI, skin phototoxicity at the MR imaging doses, T1, T2 relaxitivity, intracellular localization, and general toxicology. Finally, we will define the biodistribution of the most effective conjugates by using C-14 labeled analogs of the most effective candidates. The development of a tumor-avid contrast medium for MRI would by jtself represent an important step in the diagnosis of cancer, but a dual function agent presents the potential for a diagnostic body scan followed by targeted photodynamic therapy, combining two modalities into a single cost-effective "see and treat" approach.