Development/Bifunctional MR Agents/Diagnosis and Therapy

描述（由申请人提供）： 在我们最初的研究中，一种有效的光敏剂HPPH（一种叶绿素-a衍生物）与Gd（III）-氨基苯基DTPA（一种成像剂）缀合。在体内反射光谱证实，HPPH-aminophenylDTPA Gd（III）共轭物的肿瘤摄取高于单独的HPPH在辐射诱导的纤维肉瘤（RIF）肿瘤的C3 H小鼠。大鼠皮下植入的Ward结肠癌在静脉内注射缀合物后24小时显示出显著增加的MRI信号。在体外（RIF tum 6 r细胞）和体内（携带RIF肿瘤的小鼠），缀合物均产生显著的功效。我们还合成了一种“更高有效载荷”的分子[每个HPPH分子两个Gd（III）原子]，其也保持了亲肿瘤性、PDT活性，并且比相关的单Gd（III）类似物具有改善的MRI增强能力。不幸的是，在MRI剂量（10 mmol/kg）下，这些缀合物产生严重的皮肤光毒性。然而，用PEG基团代替焦脱镁叶绿酸-α的己基，在注射后8小时产生显著的肿瘤增强，显著的杀肿瘤活性（在第90天80%的小鼠无肿瘤），与相关的己基醚类似物相比具有降低的皮肤光毒性。通过脂质体制剂解决了这些缀合物的水溶性差的问题。 我们在此提出制备这些菌绿素类似物的Gd（III）DTP缀合物，所述菌绿素类似物在750-800 nm附近表现出长波长吸收（用于治疗较大的肿瘤）并且在肿瘤亲合力方面上级HPPH。缀合物的比较研究将包括：通过体内反射光谱法的肿瘤摄取、体外和体内PDT功效、通过体内MRI的肿瘤增强（成像）、在MR成像剂量下的皮肤光毒性、T1、T2弛豫、细胞内定位和一般毒理学。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缀合物的生物分布。 用于MRI的亲肿瘤造影剂的开发本身将代表癌症诊断中的重要步骤，但是双功能试剂呈现了诊断性身体扫描随后靶向光动力疗法的潜力，将两种模式组合成单一的具有成本效益的“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.