**Question:** A 70 year old male presented with excessive fatigue, fever & bleeding from gums while brushing. O/E- he has splenomegaly. CBC shows marked pancytopenia with presence of blasts. t(15;17)(q22;q12) cytogenetic rearrangement is found in this patient. Which of the following agents will you use in management of this patient?

A. Anthracycline
B. HDAC inhibitor
C. FLT3 inhibitor
D. FLT3 inhibitor and HDAC inhibitor

**Core Concept:** The t(15;17)(q22;q12) is a chromosomal abnormality that occurs in acute myeloid leukemia (AML) patients. It leads to the fusion protein PML-RARα, which disrupts the normal function of the retinoic acid receptor (RARα), resulting in uncontrolled proliferation of myeloid cells and impaired differentiation of leukemic cells.

**Why the Correct Answer is D:**

The correct answer is D (FLT3 inhibitor and HDAC inhibitor) because:

- Anthracycline (option A) is a chemotherapeutic agent primarily targeting topoisomerase II, which plays a crucial role in DNA replication and repair. While effective in treating AML, anthracycline therapy may not be sufficient in cases with t(15;17) translocation due to the resistance conferred by the PML-RARα fusion protein.

- HDAC inhibitors (option B) work by modulating histone and non-histone proteins, enhancing the expression of tumor suppressor genes and silencing oncogenes. HDAC inhibitors can potentially sensitize AML cells to cytotoxic agents like anthracyclines, making them more effective in treating AML.

- FLT3 inhibitors (option C) are targeted therapies that directly target the FLT3 receptor tyrosine kinase, which is frequently mutated in AML patients. FLT3 inhibitors can improve the response to cytotoxic therapy by modulating the FLT3 receptor.

- Combining an FLT3 inhibitor and an HDAC inhibitor (option D) ensures a more comprehensive approach to treating AML patients with t(15;17) translocation. By targeting both the FLT3 receptor and enhancing cytotoxic therapy sensitivity via HDAC inhibition, this combination therapy can achieve better overall response rates and potentially improve survival in such patients.

**Why Other Options are Incorrect:**

- Anthracycline (option A) alone may not be effective in treating AML patients with t(15;17) translocation due to the resistance conferred by the PML-RARα fusion protein.
- HDAC inhibitor alone (option B) might not be sufficient to improve the overall response rate and survival of AML patients with t(15;17) translocation.
- FLT3 inhibitor alone (option C) may not be effective due to the presence of the PML-RARα fusion protein, which contributes to the disease's resistance to targeted therapies like FLT3 inhibitors alone.

**Clinical Pearl:**

In AML patients with t(1