Pembrolizumab (Keytruda^®), is a checkpoint inhibitor that binds programmed death 1 (PD-1) receptor.¹ This action blocks the ability of cancer cells to turn off immune system cells and avoid elimination.¹ Pembrolizumab (Keytruda^®) is projected to be the number-one selling drug worldwide with sales of about $25 billion in 2024.²  The United State (U.S.) Food and Drug Administration (FDA) granted the first pembrolizumab (Keytruda^®) indication in 2015 for second-line treatment for unresectable, metastatic melanoma.³ To date, pembrolizumab (Keytruda^®) is FDA approved for 39 indications across multiple tumor types and hematologic cancers.¹ Nivolumab (Opdivo^®) and daratumumab and hyaluronidase-fihj (Darzalex Faspro^®) are two additional targeted cancer drugs that also rank in the top 10 best-selling drug list. ^{2, 4, 5}

Targeted cancer medications have enhanced clinical outcomes and changed treatment management.^{6, 7} The annual wholesale acquisition cost (WAC) for the three cancer drugs in the best-selling drug list are $192,735 (pembrolizumab [Keytruda^®], $198,500 nivolumab [Opdivo^®], and $222,941 daratumumab and hyaluronidase-fihj [Darzalex Faspro^®].⁸ With continued indication expansions in earlier cancer stages, incremental price increases and projected increases in cancer rates, it is unlikely that the current sales trend will change soon.^{8, 9}

Another event that will likely maintain the demand for two of the top sellers is reformulation from intravenous (IV) to subcutaneous (SC) preparations.^{2, 10}