This justified exploring the therapeutic potential of the non-optimized antibody, with the anticipation that promising results could be further enhanced through optimization. This study provides valuable insights into the evaluation of [131I]I-ERIC1s efficacy, safety, and side effects, which serve as crucial criteria for the assessment of the viability of a radiopharmaceutical theranostic agent. Efficacy: While [131I]I-ERIC1 exhibited promising therapeutic effects, its safety profile warrants careful consideration. specific activity of 15 TBq/mmol. Tumor activity peaked at 31.5 6.6% ID/g after four days, demonstrating significant antitumor efficacy, which resulted in sustained remission and extended survival. Hematological toxicity was observed, with the optimal dose identified as 2 MBq per animal administered two days post implantation. [131I]I-ERIC1 shows promise as a theranostic agent for personalized cancer Eletriptan treatment by effectively targeting SCLC tumors with manageable side effects. However, further studies are required to optimize dosing strategies and minimize toxicity. Keywords:nuclear medicine, theranostics, SCLC, biokinetics, anti-NCAM antibody, ERIC1, I-131, mice, tumor growth inhibition == 1. Introduction == Lung cancer is the second most commonly diagnosed cancer worldwide, accounting for approximately 12% of annual global cancer cases. Small cell lung cancer (SCLC) represents nearly 13% of all lung cancers and has a disheartening five-year survival rate of around 7%. Patients diagnosed at an early stage have a more favorable five-year survival rate of nearly 30%. Approximately 70% of patients present with metastatic lesions at the time of diagnosis. The current standard treatment for SCLC includes chemotherapy, chemoradiotherapy, or chemotherapy Eletriptan combined with immunotherapy. However, most patients experience relapse and require second-line chemotherapy, which is associated with a very poor prognosis. This highlights the urgent need for new diagnostic and therapeutic tools to treat SCLC [1,2]. A new strategy that appropriately addresses this challenging issue and has been successfully applied in nuclear medicine is the use of theranostics. The term theranostics refers to the Eletriptan development of more specific, individualized therapies that combine diagnostic and therapeutic capabilities into a single pharmaceutical agent. Radiotheranostics is a tailored application of theranostics in nuclear medicine, using radionuclide-labeled substances (radiotheranostic agents). The success of this strategy requires both an appropriate carrier molecule and a target structure on or within the tumor cell. The therapeutic effect relies on a cytotoxic radioisotope ( particles, particles, or Auger electron emitters), while the diagnostic component uses gamma-ray emissions, which can be detected by single-photon emission computed tomography (SPECT) or PET [3,4]. When considering potential targets, neural cell adhesion molecule 1 (NCAM1 (CD56)) emerges as promising. In 1976, Rutishauser et al. first described this surface molecule as number 56 in the Cluster of Differentiation (CD) [5]. NCAM1 (CD56) was subsequently detected in various tumors of neuroectodermal origin, such as neuroblastoma; rhabdomyosarcoma; various brain tumors; and, notably, small cell lung carcinoma [6,7,8]. Several authors [9,10,11,12] have reported that NCAM1 is expressed in the vast majority of small cell lung carcinomas. Antibodies have proven to be effective vehicles for the targeting of NCAM1, and various antibodydrug conjugates have been developed to deliver cytotoxic substances specifically to small cell lung carcinoma cells via NCAM1 targeting [11,13,14]. In this study, a similar approach is employed, whereby radionuclide I-131 serves as the cytotoxic agent, forming the basis for an experimental theranostic approach [15]. Iodine-131 can be considered a theranostic agent because it possesses both therapeutic and diagnostic properties. As a radionuclide, I-131 emits beta particles, which exert a cytotoxic effect by damaging the DNA of targeted cancer cells, leading to cell death. Concurrently, I-131 emits gamma rays, which can be detected by imaging techniques such as single-photon emission computed tomography (SPECT). The gamma radiation emitted by I-131 allows for the measurement of the radionuclide in organ or tissue samples during Eletriptan animal experiments, without significant attenuation caused by interaction with matter. This dual functionality enables simultaneous tumor treatment and monitoring of the therapeutic response, Rabbit Polyclonal to PRKY making I-131 a prime example of a theranostic agent [16]. Decades of experience support this approach, particularly in the radioiodine therapy of benign and malignant thyroid diseases [17]. In our research group, antibody ERIC1 has proven to be a promising vehicle for the targeting of the NCAM1 receptor in tumor tissues. ERIC1 is an IgG1 immunoglobulin with light chains classified under Cluster I of monoclonal anti-NCAM antibodies. It exhibits high specificity for NCAM1 [18,19,20]. In our previous work using a mouse model with neuroblastomas, we demonstrated reversible, high-affinity binding of I-131-labeled ERIC1 to NCAM1, with Kdvalues of 9 108M [21]. Notably, NCAM-positive tumors, particularly neuroblastomas, exhibited significant tumor accumulation and tumor growth inhibition after the application of this radioimmunoconjugate (RIC) [21,22]. This retention of radioactivity could be displaced by the co-administration of a cold antibody. The present study aimed to investigate whether RIC [131I]I-ERIC1 demonstrates similarly Eletriptan impressive performance in SCLC, particularly in terms of tumor accumulation and antibody-mediated radiation effects on tumor growth. == 2. Results == == 2.1. Radioactive Antibodies == Labelling.