The FDA has granted orphan drug designation to silmitasertib for the treatment of biliary tract cancer.

With no globally accepted treatments currently available for the rare cancer, this breakthrough brings hope that silmitasertib will meet the significant need for new options.
Developed by pharmaceutical firm Senhwa, silmitasertib is a highly selective inhibitor of the gene casein kinase 2, aka CK2. The drug is currently under development in several adult and paediatric oncology programmes aimed at treating recurrent, advanced, or metastatic cancer. So far, 3 phase I trials and 1 phase II trial have been completed, as well as two ongoing phase II studies of silmitasertib in cancer patients. And with results from these clinical studies showing that silmitasertib is safe, well-tolerated in humans, and easily administered orally, so far so good.

“Pre-clinical studies demonstrate that inhibition of CK2 by silmitasertib prevents DNA repair, induces apoptosis, and improves the antitumor activity of gemcitabine and cisplatin,” states Senhwa.

So, what actually is orphan drug designation? Well, in the medical world, medicines for rare diseases are termed ‘orphan medicines’. And supporting the development and evaluation of new treatments for rare diseases is a key priority for the FDA. So, the US regulator has the authority to grant orphan drug designation to any drug or biological product that is intended to treat, prevent or diagnose a life-threatening or chronically debilitating rare disease, meaning it must occur in fewer than 200,000 people in the US. Orphan drug designation gives researchers certain financial incentives to support clinical development, including the potential for up to 7 years of market exclusivity in the US, once approved by the FDA.

Biliary tract cancer represents just 3% of all gastrointestinal cancers. But as a heterogeneous group of malignancies arising from the biliary ducts, biliary tract cancer is known by more than one name. The different types of this rare disease are based on where the cancer originates. They include intrahepatic cholangiocarcinoma, extrahepatic cholangiocarcinoma, gallbladder cancer, and ampullary cancer.

People diagnosed with any of these rare cancers face extremely poor prognoses and an unacceptably low number of treatment options. So, the development of drugs like silmitasertib really can’t come fast enough.

“We are pleased to receive [orphan drug designation] for silmitasertib for the treatment of biliary tract cancer, a rare, malignant disease for which there are no effective therapies,” Mei-Hui Kuo, acting CEO of Senhwa Biosciences, said in a company-issued press release. “Orphan drug designation represents an important regulatory milestone that has the potential to expedite the clinical development of silmitasertib.”

A chemotherapy regimen of gemcitabine and the intravenous drug cisplatin is the standard first-line treatment for locally advanced and metastatic biliary tract cancers. And if this fails, second-line chemotherapy offers very little benefit. With liver cancer, which includes intrahepatic cholangiocarcinoma along with hepatocellular carcinoma, set to become the third leading cause of cancer death in both men and women by 2040, this isn’t good enough.

Luckily, silmitasertib is not alone in the race to gain FDA approval to treat rare cancers. In the last two years, the FDA approved three drugs for cholangiocarcinoma. The FGFR inhibitors pemigatinib and infigratinib gained accelerated approval for treatment of previously treated, advanced FGFR2 fusion positive cholangiocacarcinoma. The IDH1 inhibitor ivosidenib gained approval in patients with previously treated, advanced IDH1-mutant cholangiocarcinoma. The FDA also granted Breakthrough Therapy Designation for futibatinib in cholangiocarcinoma tumors positive for FGFR2 gene mutations.

The time to act is now. With more awareness comes more funding. With more funding comes more research. With more research comes more treatment options. And with more treatment options comes more hope.

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