A majority (83%) of the 150 doctors who took part in the survey by market research firm InCrowd said they would prescribe a biosimilar if it were 25% cheaper than the reference product, while only 33% said they would take such action if the drug in question was 5% cheaper.
The finding combined with prices seen so far - Zarxio is 15% cheaper than Neupogen - suggests US biosimilar prescribing will grow according to an InCrowd spokeswoman, who told us a broad cross section of doctors had taken part in the research.
“Each respondent has been in practice between 3 and 39 years. Respondents were triple-verified, have personally treated patients with biologics therapies, and were familiar with biosimilars treatments.”
Another key finding was that nearly half of respondents expect to prescribe biosimilars to a greater proportion of their treatment-naïve patients than to patients currently or previously treated with the originator biologics, 30% and 38%, respectively.
Both findings are in keeping with the conclusion of research conducted in Norway, which indicates that while discounts encourage biosimilar prescribing rates some 'brand loyalty' is inevitable.
Substitution hints
The survey also indicated a minority of physicians (20%) are likely prohibit pharmacy-level substitution.
In contrast 30% said they will never block switching and 40% will determine whether to allow a biosimilar to be issued in place of a reference drug on a case-by-case basis.
Despite State-to-State differences, in general US pharmacies can only give a patient a biosimilar in place of a reference drug if granted permission to do so by the prescribing physician.
In contrast, an interchangeable biosimilar – defined as “expected to produce the same clinical result as the reference product in any given patient” - can be substituted without the intervention unless switching is prohibited by the prescribing physician.
But, although the InCrowd survey suggests routinely blocking substitution will be rare, more data is needed.
The InCrowd spokesperson said: “With 30 respondents in each specialty, even if we did drill down into responses from the states with pending or active interchangeability legislation, we would have needed a larger sample size to assert meaningful conclusions.”
Insurance pressure
The final major finding is that 40% of physicians survey believe “insurance and reimbursement considerations ultimately will determine, if not mandate, their prescribing patterns.”
This is also in keeping with earlier research, notably analysis by Francis Megerlin from the Berkeley Center for Health Technology.
He told us last year that: “Insurers have an interest to enter and negotiate prices in the most competitive corridor, which would be defined according to the number of products competing, and by state laws that govern substitution.”