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Table 1 Recruitment rates from a sample of Phase II and Phase III Alzheimer's disease clinical trials

From: Addressing the challenges to successful recruitment and retention in Alzheimer's disease clinical trials

 

Treatment under study

Study enrollment

Sites

Enrollment, months

RRa

Screened

Screen ratiob

Mild cognitive impairment

Rofecoxib [54]

1,457

46

24

1.32

2,849

1.95

 

Rivastigmine [55]

1,018

65

12

1.30

1,526

1.50

 

Two studies of galantamine [56]

2,057

177

12

0.97

2,759

1.35

 

Donepezil [57]

270

22

16

0.77

588

2.18

 

Vitamin E and donepezil [38]

790

69

23

0.49

2,264

2.87

 

TRIMCI study of trifusal [7]

257c

29

24

0.36

NA

NA

 

Donepezil [58]

821

91

28

0.32

2,037

2.48

Mild-to-moderate AD

Dimebon [59]

183

11

6

2.77

230

1.26

 

Idebenone [60]

536

39

12

1.14

729

1.36

 

DHA (Joseph Quinn, personal communication)

402

52

8

0.96

555

1.39

 

AN1792 [61]

372

28

16

0.83

NA

NA

 

Rofecoxib [37]

351

40

11

0.80

474

1.35

 

Tarenfl urbil [9]

1,684

133

21

0.60

2,408

1.43

 

Gamma secretase inhibitor [62]

51

6

51

0.57

71

1.39

 

Rivastigmine patch [63, 64]

1,195

100

22

0.54

1,464

1.22

 

Bapineuzumab [10]

234

30

16

0.49

317

1.35

 

Rosiglitazone [65]

518

67

17

0.45

687

1.33

 

High-dose B vitamin [66]

409

40

27

0.26

601

1.47

 

Estrogen replacement [6]

120

39

32

0.10

153

1.27

Moderate-to-severe/Severe AD

Memantine [13]

404

37

6

1.82

589

1.46

 

Memantine [12]

252

32

9

0.875

345

1.37

 

Memantine [67]

350

35

17

0.59

547

1.56

 

Donepezil [5]

249

50

18

0.28

334

1.34

 

Donepezil [68]

343

91

44

0.09

543

1.58

  1. aRecruitment rate statistic, number of participants per site per month. Reported numbers are gross estimates from data reported in publications rather than exact calculations of recruitment rates averaged across study sites. bNumber of patients screened for every enrolled subject. cFailed to meet enrollment goals. AD, Alzheimer's disease; DHA, docosahexaenoic acid; NA, not available.