Short answer: Within weeks. The Repatha label says the biggest LDL drop after one dose came by 2 to 3 weeks, and the Leqvio label says a drop was seen within 14 days. In the label trials, LDL at week 12 was about 45% to 71% lower than on placebo, depending on the medicine, dose and trial. The Praluent and Repatha labels say LDL can be checked as early as 4 weeks after starting; Leqvio says 30 days.
Praluent (alirocumab) and Repatha (evolocumab) are antibodies that block PCSK9, a protein that removes LDL receptors from the liver. With PCSK9 blocked, the liver keeps more receptors and clears more LDL from the blood. Leqvio (inclisiran) works one step earlier: it lowers how much PCSK9 the liver makes.
The Repatha label says free PCSK9 was at its lowest within 4 hours of a single dose, and the largest LDL drop came by 2 weeks after a 140 mg dose and by 3 weeks after a 420 mg dose. The Praluent label says free PCSK9 was at its lowest within 4 to 8 hours. The Leqvio label says that after a single 284 mg dose, an LDL drop was seen within 14 days, average drops of 38% to 51% were seen from day 30 to day 180, and LDL was still about 53% lower at day 180.
The labels report the difference from placebo in the average percent change in LDL. Most people in these trials were already on a statin, so the numbers show what the shot added on top.
| Medicine and trial | Dose | Time point | Difference from placebo |
|---|---|---|---|
| Praluent, ODYSSEY COMBO I (on a statin) | 75 mg every 2 weeks | Week 12 | -46% (-45% on Praluent vs +1% on placebo) |
| Praluent, ODYSSEY CHOICE I (on a statin) | 300 mg every 4 weeks | Week 12 | -54% |
| Praluent, ODYSSEY LONG TERM (on a statin) | 150 mg every 2 weeks | Week 24 | -58% |
| Repatha, LAPLACE-2 (on a statin) | 140 mg every 2 weeks / 420 mg monthly | Week 12 | -71% / -63% |
| Repatha, FOURIER (heart disease, on a statin) | Either dose | Week 12 and week 72 | -63% and -57% |
| Leqvio, ORION-10 and ORION-11 (on a statin) | 284 mg at day 1, day 90, then every 6 months | Day 510 | -52% and -50% |
These are averages. The labels do not give a range for how much one person's LDL will fall, and the trials did not compare the medicines with each other.
The Praluent and Repatha labels say the LDL-lowering effect may be measured as early as 4 weeks after starting. Both add a timing note for the once-a-month style doses: on Praluent 300 mg every 4 weeks and Repatha 420 mg once monthly, LDL can vary between doses in some people, so the labels recommend measuring it just before the next scheduled dose.
The Leqvio label says LDL may be measured as early as 30 days after starting and at any time after that, without regard to when the last dose was given. When a lab test is booked, and what result would lead to a dose change, is up to the prescriber. For Praluent, the label allows a change to 150 mg every 2 weeks if the response is not enough.
Because the timing of the blood draw matters on monthly doses, it helps to know the exact date of the last shot when a result comes back. Dose Track logs each injection with its date and site, and lab results can be kept next to them, so it is easy to see whether a test was drawn just before a dose or right after one.
Read more on Dose Track: Praluent dosing schedule · Repatha dosing schedule · Leqvio dosing schedule · Praluent vs Repatha · LDL cholesterol