**Core Concept**
The T315I mutation is a type of BCR-ABL kinase domain mutation that confers resistance to most tyrosine kinase inhibitors (TKIs) used in the management of Chronic Myeloid Leukemia (CML). This mutation affects the ATP-binding site of the BCR-ABL protein, rendering many TKIs ineffective.

**Why the Correct Answer is Right**
The T315I mutation is particularly challenging to treat due to its high resistance profile. Ponatinib, a second-generation TKI, has been shown to have activity against this mutation. Ponatinib works by inhibiting the BCR-ABL kinase domain, thereby preventing the phosphorylation of tyrosine residues and the subsequent activation of downstream signaling pathways. This results in the inhibition of cell proliferation and induction of apoptosis in CML cells harboring the T315I mutation.

**Why Each Wrong Option is Incorrect**
* **Option A:** Imatinib, a first-generation TKI, is not effective against the T315I mutation due to its high resistance profile.
* **Option B:** Dasatinib, a second-generation TKI, also has limited activity against the T315I mutation.
* **Option D:** Nilotinib, another second-generation TKI, has similar limitations in treating CML with the T315I mutation.

**Clinical Pearl / High-Yield Fact**
It is essential to note that ponatinib is not without its own set of side effects and toxicities, including pancreatitis and hepatotoxicity. Therefore, its use should be reserved for patients with the T315I mutation who have failed or are intolerant to other TKIs.

**Correct Answer:** C. Ponatinib