Background: Colorectal cancer (CRC) is a commonly diagnosed cancer. We present an intriguing case of metastatic colon cancer, with a rare mutation in Isocitrate Dehydrogenase (IDH)-1, responsive to Ivosidenib. Case Presentation: A 37-year-old male, with no past medical history, presented with generalized, dull, non-radiating abdominal pain for 2 weeks. It was associated with reduced appetite, & alternating constipation with loose, non-bloody stools. On examination, he had tachycardia. Abdomen was distended & diffusely tender. Initial lab investigation showed leukocytosis with neutrophilic predominance. CT abdomen demonstrated extensive peritoneal carcinomatosis & hypodense lesions in the liver (Figure 1). Tumor markers were elevated with alpha-fetoprotein at 2.9 ng/mL, carcinoembryonic antigen at 30.3, & cancer antigen 19-9 at 73.6 U/mL. Paracentesis drained 6 liters of fluid which showed reactive mesothelial cells & mucinous pools in a hemorrhagic background. Colonoscopy revealed a large mass in the ascending colon. Biopsy was diagnostic for metastatic-moderately differentiated mucinous adenocarcinoma. He underwent total colectomy, end ileostomy, & hyperthermic intraperitoneal chemotherapy (HIPEC). FOLFOX (folinic acid, fluorouracil, & oxaliplatin) was started, but a new metastatic lesion in the liver was found. In the interim, NGS was positive for IDH-1 & BRAF mutation. Since he was progressing, target therapy with Ivosidenib was added for IDH-1, as per NGS. At 2 year follow up, he is in remission. In case of failure, our next plan is to add encorafenib targeting BRAF mutation. Discussion: 1,918,030 new cancer cases and 609,360 cancer deaths are projected in the US, by 2022. Several oncogenes and tumor suppressor genes are involved in CRC development, such as KRAS, APC, TP53, & CDKN2A. Aberrant activity of genes affects the expression of metabolic enzymes. Mutation of IDH-1 & 2 increases 2-hydroxyglutarate (2-HG), which reduces oxidative decarboxylation of alpha-ketoglutarate- an oncometabolite. IDH-1 is usually associated with AML, cholangiocarcinoma, & leukemia, but has a weak association with CRC (∼0.9%). Ivosidenib, an IDH1 inhibitor, lowers 2-HG levels. It has been approved for leukemia, but its role in CRC is yet to be explored. Conclusion: With this case report, our aim is to emphasize on the role of NGS in developing personalized cancer treatment plans in advanced malignancies and to highlight the role of Ivosidenib IDH-1 positive CRCs.