专肽生物_定制多肽合成服务_多肽合成定制服务_多肽合成厂家_多肽合成公司

FAPI-34 是一种成纤维细胞激活蛋白 (FAP) 抑制剂，具有良好的药代动力学和生化特性。

FAP是一种II型跨膜糖蛋白，属于二肽基肽酶IV样家族的丝氨酸蛋白酶，这类蛋白酶通过脯氨酰切割作用表达于CAF细胞表面形成二聚体。因此，FAP成为极具潜力的诊断和治疗靶点。它在调节细胞外基质方面发挥着复杂作用。与其他二肽基肽酶家族成员不同，FAP在变性胶原蛋白中具有凝胶酶活性，尤其当被基质金属蛋白酶切割时表现显著。

大多数上皮肿瘤会招募成纤维细胞等非恶性细胞，并将其激活为癌相关成纤维细胞。这一过程常导致膜丝氨酸蛋白酶成纤维细胞活化蛋白（FAP）的过度表达。研究表明，携带DOTA的FAP抑制剂（FAPIs）能通过PET/CT扫描生成高对比度图像。由于SPECT作为成本更低、应用更广泛的PET替代方案，99mTc标记的FAPIs成为适用于更多患者影像诊断的理想示踪剂。

FAPI（氟代氨基丙酸）作为新型示踪剂，可用于评估和治疗多种癌症，除了FAPI造影剂的诊断价值外，其在放射性核素治疗患者筛选中的潜在应用前景同样引人注目。针对FAP蛋白设计的177Lu标记内化抗体在临床前模型中已验证有效。对于具有高摄取率但生物半衰期较短的造影剂，采用物理半衰期较短的放射性核素可能比使用长寿命放射性核素更为合适。基于这些考量，研究者在临床前阶段使用64Cu对FAPI类似物进行了评估。64Cu与67Cu的组合堪称诊疗一体化的创新方案：64Cu作为正电子发射放射性同位素，半衰期达12.7小时，既支持诊断示踪剂的集中生产和分发，又便于开展前瞻性剂量测定；而67Cu虽与177Lu具有相似的物理特性，但半衰期更短。相较于68Ga-FAPI-04,64Cu-FAPI-04在肝脏和肠道显示出更高的活性。尽管已知靶向成分相同的放射性金属会影响生物分布，但对于铜元素而言，DOTA的弱螯合作用可能导致肝脏中游离64Cu的摄取增加。而对于放射性肽类药物，选用其他螯合剂可显著降低肝脏活性。然而，除非与游离铜有关，改变从快速肾脏清除到较慢的肝胆排泄的清除率可能会通过增加放射性配体的生物利用度而有利于治疗应用。

HT-1080-FAP异种移植小鼠体内99mTc-FAPI-34的生物分布(A)及放射性示踪剂注射后1小时和4小时的肿瘤组织比(B)。每个时间点n=5-6

FAPI-34因其快速肿瘤摄取和体内快速清除特性而具有高对比度，可能成为闪烁显像的理想选择。由于该螯合剂支持188Re标记，该示踪剂也可用于FAP高表达的结缔组织瘤内放射治疗。

同时我们自主设计开发了FAPI-34的一种合成路线，并取得不错了收率。

参考文献

[1] DOI: 10.2967/jnumed.119.239731

[2] https://doi.org/10.3390/ijms24043863

[3] DOI: 10.2967/jnumed.120.256271

定义
酶是用于生化反应的非常有效的催化剂。它们通过提供较低活化能的替代反应途径来加快反应速度。酶作用于底物并产生产物。一些物质降低或什至停止酶的催化活性被称为抑制剂。
发现
1965年，Umezawa H分析了微生物产生的酶抑制剂，并分离出了抑制亮肽素和抗痛药的胰蛋白酶和木瓜蛋白酶，乳糜蛋白酶抑制的胰凝乳蛋白酶，胃蛋白酶抑制素抑制胃蛋白酶，泛磷酰胺抑制唾液酸酶，乌藤酮抑制酪氨酸羟化酶，多巴汀抑制多巴胺3-羟硫基嘧啶和多巴胺3-羟色胺酶酪氨酸羟化酶和多巴胺J3-羟化酶。最近，一种替代方法已应用于预测新的抑制剂：合理的药物设计使用酶活性位点的三维结构来预测哪些分子可能是抑制剂1。已经开发了用于识别酶抑制剂的基于计算机的方法，例如分子力学和分子对接。
结构特征
已经确定了许多抑制剂的晶体结构。已经确定了三种与凝血酶复合的高效且选择性的低分子量刚性肽醛醛抑制剂的晶体结构。这三种抑制剂全部在P3位置具有一个新的内酰胺部分，而对胰蛋白酶选择性最高的两种抑制剂在P1位置具有一个与S1特异性位点结合的胍基哌啶基。凝血酶的抑制动力学从慢到快变化，而对于胰蛋白酶，抑制的动力学在所有情况下都快。根据两步机理2中稳定过渡态络合物的缓慢形成来检验动力学。
埃米尔•菲舍尔（Emil Fischer）在1894年提出，酶和底物都具有特定的互补几何形状，彼此恰好契合。这称为“锁和钥匙”模型3。丹尼尔·科什兰（Daniel Koshland）提出了诱导拟合模型，其中底物和酶是相当灵活的结构，当底物与酶4相互作用时，活性位点通过与底物的相互作用不断重塑。
在众多生物活性肽的成熟过程中，需要由其谷氨酰胺（或谷氨酰胺）前体形成N末端焦谷氨酸（pGlu）。游离形式并与底物和三种咪唑衍生抑制剂结合的人QC的结构揭示了类似于两个锌外肽酶的α/β支架，但有多个插入和缺失，特别是在活性位点区域。几种活性位点突变酶的结构分析为针对QC相关疾病5的抑制剂的合理设计提供了结构基础。
作用方式
酶是催化化学反应的蛋白质。酶与底物相互作用并将其转化为产物。抑制剂的结合可以阻止底物进入酶的活性位点和/或阻止酶催化其反应。抑制剂的种类繁多，包括：非特异性，不可逆，可逆-竞争性和非竞争性。可逆抑制剂 以非共价相互作用（例如疏水相互作用，氢键和离子键）与酶结合。非特异性抑制方法包括最终使酶的蛋白质部分变性并因此不可逆的任何物理或化学变化。特定抑制剂 对单一酶发挥作用。大多数毒药通过特异性抑制酶发挥作用。竞争性抑制剂是任何与底物的化学结构和分子几何结构非常相似的化合物。抑制剂可以在活性位点与酶相互作用，但是没有反应发生。非竞争性抑制剂是与酶相互作用但通常不在活性位点相互作用的物质。非竞争性抑制剂的净作用是改变酶的形状，从而改变活性位点，从而使底物不再能与酶相互作用而产生反应。非竞争性抑制剂通常是可逆的。不可逆抑制剂与酶形成牢固的共价键。这些抑制剂可以在活性位点附近或附近起作用。
功能
工业应用中， 酶在商业上被广泛使用，例如在洗涤剂，食品和酿造工业中。蛋白酶用于“生物”洗衣粉中，以加速蛋白质在诸如血液和鸡蛋等污渍中的分解。商业上使用酶的问题包括：它们是水溶性的，这使得它们难以回收，并且一些产物可以抑制酶的活性（反馈抑制）。
药物分子，许多药物分子都是酶抑制剂，药用酶抑制剂通常以其特异性和效力为特征。高度的特异性和效力表明该药物具有较少的副作用和较低的毒性。酶抑制剂在自然界中发现，并且也作为药理学和生物化学的一部分进行设计和生产6。
天然毒物 通常是酶抑制剂，已进化为保护植物或动物免受天敌的侵害。这些天然毒素包括一些已知最剧毒的化合物。
神经气体（ 例如二异丙基氟磷酸酯（DFP））通过与丝氨酸的羟基反应生成酯，从而抑制了乙酰胆碱酯酶的活性位点。
参考
1、Scapin G (2006). Structural biology and drug discovery. Curr. Pharm. Des.,      12(17):2087–2097.
2、Krishnan R, Zhang E, Hakansson K, Arni RK, Tulinsky A, Lim-Wilby MS, Levy OE, Semple JE, Brunck TK (1998). Highly selective mechanism-based thrombin inhibitors:  structures of thrombin and trypsin inhibited with rigid peptidyl aldehydes. Biochemistry, 37 (35):12094-12103.
3、Fischer E (1894). Einfluss der configuration auf die wirkung der enzyme. Ber. Dt. Chem. Ges., 27:2985–2993.
4、Koshland DE (1958). Application of a theory of enzyme specificity to protein synthesis. PNAS., 44 (2):98–104.
5、Huang KF, Liu YL, Cheng WJ, Ko TP, Wang AH (2005). Crystal structures of human glutaminyl cyclase, an enzyme responsible for protein N-terminal pyroglutamate formation. PNAS., 102(37):13117-13122.
6、Holmes CF, Maynes JT, Perreault KR, Dawson JF, James MN (2002). Molecular enzymology underlying regulation of protein phosphatase-1 by natural toxins. Curr Med Chem., 9(22):1981-1989.

Definition
Enzymes are very efficient catalysts for biochemical reactions. They speed up reactions by providing an alternative reaction pathway of lower activation energy. Enzyme acts on substrate and gives rise to a product. Some substances reduce or even stop the catalytic activities of enzymes are called inhibitors.

Discovery
In 1965, Umezawa H analysed enzyme inhibitors produced by microorganisms and isolated leupeptin and antipain inhibiting trypsin and papain, chymostatin inhibiting chymotrypsin, pepstatin inhibiting pepsin, panosialin inhibiting sialidases, oudenone inhibiting tyrosine hydroxylase, dopastin inhibiting dopamine 3-hydroxylase, aquayamycin and chrothiomycin inhibiting tyrosine hydroxylase and dopamine J3-hydroxylase . Recently, an alternative approach has been applied to predict new inhibitors: rational drug design uses the three-dimensional structure of an enzyme's active site to predict which molecules might be inhibitors 1. Computer-based methods for identifying inhibitor for an enzyme have been developed, such as molecular mechanics and molecular docking.

Structural Characteristics
The crystal structures of many inhibitors have been determined. The crystal structures of three highly potent and selective low-molecular weight rigid peptidyl aldehyde inhibitors complexed with thrombin have been determined. All the three inhibitors have a novel lactam moiety at the P3 position, while the two with greatest trypsin selectivity have a guanidinopiperidyl group at the P1 position that binds in the S1 specificity site. The kinetics of inhibition vary from slow to fast with thrombin and are fast in all cases with trypsin. The kinetics are examined in terms of the slow formation of a stable transition-state complex in a two-step mechanism 2.

Emil Fischer in 1894 suggested that both the enzyme and the substrate possess specific complementary geometric shapes that fit exactly into one another.This is known as "the lock and key" model 3. Daniel Koshland suggested induced fit model where substrate and enzymes are rather flexible structures, the active site is continually reshaped by interactions with the substrate as the substrate interacts with the enzyme 4.

N-terminal pyroglutamate (pGlu) formation from its glutaminyl (or glutamyl) precursor is required in the maturation of numerous bioactive peptides. The structure of human QC in free form and bound to a substrate and three imidazole-derived inhibitors reveals an alpha/beta scaffold akin to that of two-zinc exopeptidases but with several insertions and deletions, particularly in the active-site region. The structural analyses of several active-site-mutant enzymes provide a structural basis for the rational design of inhibitors against QC-associated disorders 5.

Mode of Action
Enzymes are proteins that catalyze chemical reactions. Enzymes interact with substrate and convert them into products. Inhibitor binding can stop a substrate from entering the enzyme's active site and/or hinder the enzyme from catalyzing its reaction. There are a variety of types of inhibitors including: nonspecific, irreversible, reversible - competitive and noncompetitive. Reversible inhibitors bind to enzymes with non-covalent interactions like hydrophobic interactions, hydrogen bonds, and ionic bonds. Non-specific methods of inhibition include any physical or chemical changes which ultimately denature the protein portion of the enzyme and are therefore irreversible. Specific Inhibitors exert their effects upon a single enzyme. Most poisons work by specific inhibition of enzymes. A competitive inhibitor is any compound which closely resembles the chemical structure and molecular geometry of the substrate. The inhibitor may interact with the enzyme at the active site, but no reaction takes place. A noncompetitive inhibitor is a substance that interacts with the enzyme, but usually not at the active site.  The net effect of a non competitive inhibitor is to change the shape of the enzyme and thus the active site, so that the substrate can no longer interact with the enzyme to give a reaction. Non competitive inhibitors are usually reversible. Irreversible Inhibitors form strong covalent bonds with an enzyme.  These inhibitors may act at, near, or remote from the active site .

Functions
Industrial application, enzymes are widely used commercially, for example in the detergent, food and brewing industries. Protease enzymes are used in 'biological' washing powders to speed up the breakdown of proteins in stains like blood and egg. Problems using enzymes commercially include: they are water soluble which makes them hard to recover and some products can inhibit the enzyme activity (feedback inhibition) .

Drug molecules, many drug molecules are enzyme inhibitors and a medicinal enzyme inhibitor is usually characterized by its specificity and its potency. A high specificity and potency suggests that a drug will have fewer side effects and less toxic. Enzyme inhibitors are found in nature and are also designed and produced as part of pharmacology and biochemistry 6.

Natural poisons are often enzyme inhibitors that have evolved to defend a plant or animal against predators. These natural toxins include some of the most poisonous compounds known.

Nerve gases such as diisopropylfluorophosphate (DFP) inhibit the active site of acetylcholine esterase by reacting with the hydroxyl group of serine to make an ester.

References

Scapin G (2006). Structural biology and drug discovery. Curr. Pharm. Des.,      12(17):2087–2097.

Krishnan R, Zhang E, Hakansson K, Arni RK, Tulinsky A, Lim-Wilby MS, Levy OE, Semple JE, Brunck TK (1998). Highly selective mechanism-based thrombin inhibitors:  structures of thrombin and trypsin inhibited with rigid peptidyl aldehydes. Biochemistry, 37 (35):12094-12103.

Fischer E (1894). Einfluss der configuration auf die wirkung der enzyme. Ber. Dt. Chem. Ges., 27:2985–2993.

Koshland DE (1958). Application of a theory of enzyme specificity to protein synthesis. PNAS., 44 (2):98–104.

Huang KF, Liu YL, Cheng WJ, Ko TP, Wang AH (2005). Crystal structures of human glutaminyl cyclase, an enzyme responsible for protein N-terminal pyroglutamate formation. PNAS., 102(37):13117-13122.

Holmes CF, Maynes JT, Perreault KR, Dawson JF, James MN (2002). Molecular enzymology underlying regulation of protein phosphatase-1 by natural toxins. Curr Med Chem., 9(22):1981-1989.

FAPI 多肽探针是一类以成纤维细胞活化蛋白（FAP）为靶点的小分子多肽类分子探针，核心功能是特异性结合 FAP，经标记后可用于肿瘤等疾病的成像诊断与靶向治疗。以下从核心信息、结构与标记、应用场景、优势与挑战展开说明：

1、FAPI 多肽探针核心信息
  1.1、靶点特性：FAP 在肿瘤相关成纤维细胞（CAFs）高表达，而在正常组织低表达或不表达，是肿瘤诊断与治疗的理想靶点。
  1.2、核心功能：通过与 FAP 活性位点结合实现靶向识别，结合不同标记物可用于 PET、SPECT、MRI、荧光成像等，部分还可用于核素靶向治疗。
2、FAPI 多肽探针结构与标记
结构组成：通常由 FAP 特异性结合单元（如喹啉酰胺、吡咯并三嗪衍生物等）、连接链和可修饰位点构成，可修饰位点用于引入螯合基团（如 DOTA、NOTA），进而偶联放射性核素、荧光基团或造影剂等。
3、FAPI 多肽探针常见标记类型
标记类型    常用标记物    应用场景
放射性核素    68Ga、18F、177Lu、99mTc    PET/SPECT 成像、核素治疗
荧光基团    Cy7 等近红外荧光基团    荧光成像、术中导航
造影剂    钆（Gd）    MRI 成像
4、FAPI 多肽探针应用场景
  4.1、肿瘤成像诊断：用于多种实体瘤（如肺癌、肝癌、胰腺癌等）的 PET/SPECT/MRI 成像，可清晰显示肿瘤位置、大小及转移灶，评估肿瘤负荷与治疗效果。
  4.2、术中导航：荧光标记的 FAPI 探针可帮助外科医生精准识别肿瘤边界，提高手术切除的彻底性。
  4.3、靶向治疗：177Lu 等治疗性核素标记的 FAPI 探针可实现核素靶向内照射治疗，直接杀伤肿瘤相关成纤维细胞，抑制肿瘤生长。
  4.4、其他疾病：如纤维化疾病（肝纤维化、肺纤维化）的诊断与病情评估，因为 FAP 在纤维化组织中也会异常表达。
5、FAPI 多肽探针的优势与挑战
  5.1、优势
高特异性与亲和力，对 FAP 的解离常数 Ki 多处于纳摩尔级，成像信噪比高。
部分探针具有良好的药代动力学特性，如肿瘤摄取高、滞留时间长、正常组织清除快。
适用范围广，可用于多种肿瘤与纤维化疾病。
  5.2、挑战
部分探针存在体内稳定性不足、代谢快等问题，影响成像质量与治疗效果。
不同肿瘤中 FAP 表达水平存在差异，可能导致部分肿瘤成像灵敏度不高。
临床应用中需优化标记工艺、给药剂量与成像时间，以平衡效果与安全性。
6、总结
FAPI 多肽探针凭借对 FAP 的特异性靶向能力，在肿瘤等疾病的精准诊疗中展现出巨大潜力，随着探针结构优化与标记技术进步，其临床应用前景将进一步拓展。