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Table 1 Three representative COVID-19 scenarios for a symptomatic and a disease modification trial. No in-clinic visits are allowed during a 6-month interruption from March 19 to September 19, 2020. Bold text indicates significant distinctions between the two trials

From: Impact of potential modifications to Alzheimer’s disease clinical trials in response to disruption by COVID-19: a simulation study

 

Symptomatic trial

Phase 2 symptomatic trial in mild-to-moderate AD

 • Daily oral medication

 • Planned outcomes at 12 months

 • N = 360 randomized to drug or placebo

Disease modification trial

Phase 2/3 disease modification trial for early AD

 • In-clinic monthly drug infusions

 • Planned outcomes at 18 months

 • N = 280 randomized to drug or placebo

Trial status on March 19, 2020

Fully enrolled

Fully enrolled

97.5% completed 3 months

80% completed 3 months

67% completed 6 months

50% completed 6 months

45% completed 9 months

25% completed 12 months

22% completed 12 months

12% completed 18 months

Dropout

30% dropout rate evenly distributed across visits. No discontinuation due to COVID19

24% (66 subjects) discontinued before or on March 19 (partially due to COVID19). An additional non-COVID dropout rate of 25%. Final dropout rate: 42%a

Scenario 1

Trial stopped on March 19; no further visits or data collection

Scenario 2

Outcome assessments paused during COVID interruption, resumed after interruption.

• ~ 50%, who had completed 9 months, missed their 12-month outcome

• ~ 25% missed their 9-month outcome but could have 12-month assessments

• ~ 30% missed other outcomes

Medication continued during COVID interruption.

• ~ 50%, who had completed 12 months, missed their 18-month outcome

• ~ 25% missed their 12-month outcome but could have 18-month assessments

• ~ 50% missed other outcomes

Medication infusion paused during COVID interruption, resumed after interruption.

Scenario 3

No outcomes assessed during COVID interruption.

Medication continued during COVID, with extended medication provided beyond 12 months

Up to a 3-month extension of the final assessment window, to allow completion of 12 months outcomes after clinics reopened

Outcomes assessed remotely during COVID interruption; in-clinic assessment resumed after interruption.

Medication infusion paused during COVID interruption

No extension of the final assessment window

  1. aThe original expected dropout rate is 25%. In this scenario, 66 discontinued due to COVID-19, and because some would have been “potential completers,” the final dropout rate is approximately 42%. See trial construct 2 statistical methods