Insmed Addressing Investor Inbounds

Research evidence excerpt

Insmed Addressing Investor Inbounds

reported Brinsupri sales? To translate

from Symphony Rx data to potential true underlying Rx, we need to establish an estimate

for the capture rate, the proportion of Brinsupri scripts that Symphony is picking up. To

do this we take reported sales from INSM and make an assumption about gross-to-net

(GTN). Recall that INSM has guided to mid-20%s to low-30%s for gross to net, so in

order to estimate capture, we use a fixed 30% assumption for GTN. Then, using reported

sales and that assumed net price per script, we can estimate the number of scripts that

drove the sales number. We compare this calculated script number to the Symphony Rx

figure.

• Looking back at 1Q26 and 4Q25, assuming a 30% GTN, the monthly Symphony

scripts captured an estimated ~32% of potential actual scripts. This is an estimate as

a) we don’t have precision on net price/Rx and b) it is likely that the price/Rx in 1Q

was not identical to that in 4Q. However, this estimated capture gives us something

to work with. We therefore think 32% is a reasonable estimate of Symphony’s capture

rate, but given the lack of precision we have on capture, out of conservatism we assess

scenarios for capture rates of 32%, 34%, 36%, 38%, and 40%.

• A note on capture rate assumptions… There is no guarantee that the capture rate

remains fixed as time goes on and it represents a key input when interpreting

Symphony data. When capture is this low, small changes can make a big difference.

We have seen situations where third-party capture has improved over the course of

a launch (e.g. Amvuttra). When this happens, it can lead to over-estimating the

underlying Rx volume. Should capture change significantly, it could meaningfully

impact the output of any analysis.