In an untitled letter issued last Friday and made public this week, the FDA took aim at clinical data included on a doctor-facing web page for Taiho Oncology’s Lytgobi.

Lytgobi is an FGFR inhibitor that received accelerated approval in 2022 to treat adults with previously treated, unresectable, locally advanced or metastatic cholangiocarcinoma in the liver with fibroblast growth factor receptor 2 gene fusions or other rearrangements.

The new letter takes issue with one page of the branded Lytgobi website for U.S. healthcare professionals. The “Efficacy Results” page “makes false or misleading representations about the benefits of Lytgobi” and therefore “misbrands” the drug, according to the FDA—violations that are “particularly concerning,” per the agency, because of the aggressive nature of intrahepatic bile duct cancer and the “serious risks” involved in treating it.

The FDA’s complaint stems from Taiho’s inclusion on the website of certain results from FOENIX-CCA2, a single-arm phase 2 study of daily Lytgobi use.

For one, because of the trial’s single-arm design, according to the FDA, it wouldn’t be able to definitively show improvement in time-to-event endpoints like overall survival (OS) and progression-free survival (PFS). On those two points, the agency wrote, “absent an appropriate comparator, it is not possible to determine if the observed effect is attributable to Lytgobi or to other factor(s), such as the natural history of the disease.”

The letter acknowledges that the web page does include notes near the OS and PFS data stating that they aren’t “intended to draw conclusions regarding the efficacy of LYTGOBI” and advising that the results be “interpreted with caution.” That caveat, however, isn’t enough to stop the featured data points from misleading readers, according to the FDA, since the study remains “incapable” of supporting even the suggestion that those efficacy results could be attributed to Lytgobi.

The agency also flagged the web page’s listing an 83% disease control rate (DCR), which is defined there as “the sum of complete response, partial response, and stable disease” and again cited results from FOENIX-CCA2.

The implication that Lytgobi improves DCR is “misleading,” according to the FDA, because the study “could not demonstrate this result”—once again, due to its single-arm design. That prevented the study from establishing that the stable disease results, specifically, were linked to Lytgobi and not to some other factor, per the agency.

Again, the letter acknowledged statements appearing near the DCR data noting that the results may not necessarily be attributable to Lytgobi but dismissed them as not enough to outweigh any potentially “misleading” representations.

As of publication time Wednesday, the web page still included all of the content detailed in the letter.

The FDA gave Taiho 15 working days to submit a written response either refuting the letter’s concerns or “explaining your plan for the timely discontinuation of such communications, or for ceasing distribution of Lytgobi.”

In a statement sent to Fierce Pharma Marketing, Taiho said, “We take every communication from the FDA seriously. We always strive to present data in a manner that is truthful and not misleading and consistent with FDA guidelines. We are reviewing their comments and will respond appropriately and in a timely manner.”