The FDA noted in its review of sotorasib that in phase 1 studies tumors shrank when exposed to as little as a fifth of the 960-mg daily dose Amgen selected. At all doses tested in that early trial, the drug reached roughly the same concentrations in the blood, which suggested that at higher doses the drug was mostly just intensifying side effects like diarrhea, vomiting, and mouth sores.

For most classes of drugs, companies spend considerable time in phases 1 and 2 of development, homing in on the right dosage. “No one would think of dosing a statin or antibiotic at the highest tolerable dose,” Ratain said.

Things are different in cancer drug creation, whose approach originated with chemotherapy, which damages as many cancer cells as possible, wrecking plenty of healthy tissue in the bargain. Typically, a company’s first series of cancer drug trials involve escalating doses in small groups of patients until something like a quarter of them get seriously ill. That “maximum tolerated dose” is then employed in more advanced clinical trials, and goes on the drug’s label. Once a drug is approved, a doctor can “go off-label” and alter the dosage, but most are leery of doing so.

Patients can find the experience rougher than advertised. During clinical trials, the side effects of the cancer drug osimertinib (Tagrisso) were listed as tolerable and manageable, said Jill Feldman, a lung cancer patient and advocate. “That killed me. After two months on that drug, I had lost 15 pounds, had sores in my mouth and down my throat, stomach stuff. It was horrible.”

Some practitioners, at least, have responded to the FDA’s cues on sotorasib. In the Kaiser Permanente health system, lung cancer specialists start with a lower dose of the drug, spokesperson Stephen Shivinsky said.

Smaller Doses — And Revenue

Amgen was clearly aware of the advantages of the 240-mg dosage before it sought FDA approval: It filed a provisional patent application on that dosage before the agency gave breakthrough approval for the drug at 960 mg. The company doesn’t appear to have disclosed the patent filing to investors or the FDA. McCarthy said the FDA was prohibited by law from discussing the particulars of its sotorasib regulation plans.

Switching to a 240-mg dosage could register a huge hit to Amgen’s revenue. The company markets the drug at more than $20,000 for a month of 960-mg daily doses. Each patient who could get by with a quarter of that would trim the company’s revenue by roughly $180,000 a year.

Amgen declined to comment on the patent issue or to make an official available to discuss the dosage and pricing issues.

Crosslin, who depends on Social Security for his income, couldn’t afford the $3,000 a month that Medicare required him to pay for sotorasib, but he has received assistance from Amgen and a charity that covers costs for patients below a certain income.

...continued

©2024 KFF Health News. Distributed by Tribune Content Agency, LLC.