Here's my model results that appears to be in line with HDG's current thoughts and AMRN "expectations".
Goal: Model Reduce-It primary events to determine potential event rates and RRR that meet that actual interim and end dates. The model considers the following factors:
1. Increasing event rate with age
2. Dropouts who discontinue study and are lost to follow-up
3. Varying event rates vary based on enrollment date (before & after May 2013)
Assumptions:
1. Event rate increases exponetially at 2%/year extrapolated from KPNW study for high risk patients age 60-70
2. Discontinue study & lost to followup rate (LtFu) of 3%/year (approximately 970 over the trial)
3. A range of initial placebo rates both before and after AMRN increased Trig enrollment requirements in May 2013
4. Constant RRR over time. JELIS data did not result in a conclusive pattern
5. Enrollment data per ADCOM and AMRN PRs
Results:
Conclusions:
1. Model results with 5.2% composite rate closely mimics linear "Expected" results shown by AMRN at ADCOM.
This provides confidence in the model and indicates that the effects of increasing event rates with age and reduction of the study group size (from LtFu and events) roughly cancel out.
2. The "band" of potential event rate combinations that meet all the actual interim and end dates is narrow and can be approximated with a composite average rate of 4.95%.
3. With initial placebo rates of 5% and 5.5% and secondary placebo rates (after May 2013) of 6%, the corresponding RRR is 18% and 32% respectively. My guess is illustrated by the orange line (P1i = 5.2%, P2i = 6.0%, RRR = 24%)
4. PY > 35,000 represents the total participant years of everyone remaining in the study, including those who have already had a primary event. With the above assumptions, the model results in PY = 34957 (close enough for me) through March 2018. The subset of PY elgible for primary events is approximately 32650. With no death or LtFu, PY would be approximately 38,800.
5. The event rate should increase approximately 0.5% over the course of the 5-year study resulting in in an average event rate approximately 0.25% than at the start of the study.
6. Given the duration of the study, the "bimodal" effect of enrolling lower trig participants before May 2013 and higher trig participants after May 2013 is not significant and may be closely approximately by a single average rate (the orange line is very close to the dashed black line).
7. LtFu rate assumption of 3% annually results mostly closely matches ADCOM "Expected" results shown by AMRN. If a smaller LtFu rate is assumed, the 5.2% composite rate results in 1612 events prior to the end of 2017. With a larger LtFu rate, 5.2% composite rate stretches the trial into 2018.
8. If the LtFu rate is increased to 4% or more annually, there is no straight line average event rate that meets all actual dates; either event 1290 occurs prior to March 2017 or event 1612 occurs after March 2018.