Effect of reduction in brain amyloid levels on change in cognitive and functional decline in randomized clinical trials: an updated instrumental variable meta-analysis

Al z h e i me r’s d ise a s e , a myl o i d, c ausa l e ffect, cl in i c a l trial s , c og nit ive d ecline All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprintthis version posted April 5, 2022. ; https://doi.org/10.1101/2022.04.01.22273253doi: medRxiv preprint NOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice. ABST RA CT Objec t iv e: To upd ate a rec e ntly publ i s he d analy s i s ex ploring th e cau sal a ssocia t i o n betwe e n po s i tro n e mission t o mography ( PET) -mea s ur ed chan ge i n brain β -amylo id pla que and c ognitiv e de cline i n pa tien t s w ith Alzh eimer’s di s ea se ( AD) e nr o lled in r a ndomized c linic al trial s ( RCT s ) . Design: Updat ed in s trum enta l variabl e meta -ana ly si s . Se t t i n g: Sixtee n RCT s w ere includ ed in thi s upda t e d met a- analy s i s ver su s 14 i n the orig in al pu blica t i on by Ackl ey et al. 1 Dat a s o urc e s we r e Cl inica lTrial s.o rg, Alz heime r Re se arch Fo rum (a lzforum. org) , PubMe d and cl inica l s tu dy report s f rom 2 015 t o Marc h 1, 202 2. Three r e sea r c he r s e xtract ed da ta fr om the da ta sourc e s in d epend ently and sub sequ ently re s olv ed a ny discrep an cy. Po pulation: RCT s that eva lu ate d β - a m y lo i d ta r g e ti n g t he r a pi es a n d e n r o l l e d a du l t p at i e nts wi th AD de menti a or mild co gnitive i mpairmen t due to A D w it h da t a on β - a myloi d a s m ea s ured by P ET and c linic al o ut c ome me a s u re s. Mai n outcom e me as ures : An in st r um e ntal variabl e me ta -analy s i s was pe rfo rmed to compu t e tr ial a nd drug - s pe ci fic e stima te s an d pool ed es timat e s o f the e f f e ct o f ch ang e in PET β -a myloid st andar d up t a ke v alue r atio (S UVR) on c ogni tiv e a nd fun ction al decli ne wi t h 95% c onfi den c e interval s ( CI s ) and a ssoci a ted p -val ue s. T his analy s i s upda te d a nd exp anded a pr i o r me t a -an aly s i s by Ac kley et al . 1 u s i n g the s ame me thodol og y and c linic al o ut c ome mea s ure s : Clini cal Dem e ntia R ating –Sum of Box e s (C D R - S B), Al zheime r's D i s ea se A s s e ssment Sc a le– Cog nitive Su bsc a le (AD AS- Cog ), and Mini-M ent al Sta t e E xamin ation (MMSE ). R e su l t s: The reduc tion o f PE T-me as ure d β -amy loid induce d a sta t i s tica lly s ig n ifica nt r educ t i on in c ognitiv e and func t i o nal dec lin e. T h e e ff ect s i z e w a s c ha rac te r iz ed by a n e stima te d chang e (95% CI ) of 0 .09 (0 .034 , 0.15 ) o n th e CD R -S B ; 0.33 (0.1 2, 0.55 ) on the ADAS -Cog ; and 0. 13 (0.017, 0 .24) on th e MMSE for eac h dec rea s e o f 0.1 -unit in P ET β -amy loid S U VR. Co nclusion : This updated in strumen tal va r i able meta -a n alysi s o f 16 RCTs p rovide s stati s tica lly sign ific ant e videnc e of a cau sal r el a tion sh ip betwe e n the reduc t i on in b rain β - a m yloid plaque and t he redu ctio n in cogni t i ve an d f unction a l dec line in pati ent s with Alz heime r’s dis ea se . All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprintthis version posted April 5, 2022. ; https://doi.org/10.1101/2022.04.01.22273253doi: medRxiv preprint

Alzheim e r ’s dis ea se ( AD ) is de fin ed pathologi call y by t he pre s e n ce of β -a myloid deposi ts, tau - c ontainin g n euro fibrill ary ta ngle s, neur o nal injury and d egen era tion. 2 C l i n i c a l l y , t h e d i s e as e c o u r s e i s c harac t e r ized by progre s s iv e cogni t i ve decl ine, behav ior al chan ge s, i ncrea s ed depend e ncy in ac t i v it ies o f d a i ly l i v i ng a n d i n c r e a s e d bu r d e n f or c a r e gi v e rs an d s o ci et y . 3 4 Genetic da t a , prec linic a l mo dels , biomark er s, and c linic a l ob serva tion s 5-8 have highlig hted that r e moval o f brai n par enchy mal β -am yloid rema ins a rel ev ant targe t f or s l owing dise a s e p rogre ssio n. N one t hele ss, r andomize d c linic al tri al s (RCT s) o f d r ug s t hat ta r g et the r educ tion in pr od uc tion or remov a l of β -amyloi d h av e g enera ted incon si ste nt r e s ul ts, a n d the l ink betwe en cha nge i n β -amyloid pa thology an d c ognitiv e/fun ctio nal per fo r ma nce i s ho t l y deba t e d . 9 One po s sibl e r ea son for the inc on s i s t ent ev idenc e t hat β - a m y l oi d is a c li n i c all y va l i d t ar get i n A D m ay be tha t pa tien t-l ev el c or r el a tion an a lys es b etwee n c hang e in β -am yloid a nd ch ang e i n cog nition u sin g da ta fr om a si ngl e trial may hav e in su ffi c ient sta t i stica l power and/ or con foundi n g bias . To add re s s the se limita tio n s , Ack ley et al. 1 publi sh ed a m eta -an al ysi s u sing an in s t rumen ta l v ariabl e a pp r oa ch tha t i n t e gra ted 14 RCT s wi t h dat a ava ila bl e up until April 3 0, 2020. T he RCT s wer e sel ec te d using th e Alzheim e r R e sea r c h Fo rum ( al z f orum.o rg) and f rom Cl inica lTri als .gov and r e quired qu anti tativ e me asu r e men t s o f cha nge i n a c ognitiv e sco re a nd bra in β -amyloi d data u s i n g the s t anda r di ze d up t a ke v alu e r atio ( S UVR ) ob ta ine d f rom β -amyl oid posi tr o n emis s i on to mograph y ( P ET) . The autho r s then u sed r and omiz a t i on to t r ea t m e nt g r ou p s a s the in stru ment al va r i a ble to eli mi nate co n f o unding bi as, permi tting va lid c au s al inf er enc e on the ef fec t of a verag e PET -mea sur ed β -amy loid reduc tion o n a verage c ogni tive and func tiona l dec lin e within and acr o ss multipl e s tudi e s . I n the Ackl ey et al. stu dy, 1 the po oled e stima te s cha nge s we re 0.058 (95 % CI: − 0.031 to 0 .15) an d 0. 034 (95% CI: − 0.05 6 to 0 .12) on the C li nica l Dem enti a Rat ing S cale –Sum o f Boxe s (C DR - S B) a nd Mini -M e nt a l S tat e E xamin ation (MMSE ) score s, re spec tiv ely, for e a ch 0 .1 -unit r eductio n in the PE T β - amyl oid SUVR. I n t h e i r o r i g i n a l w o r k , A c k l e y et al . 1 provided a publ icly ava ilabl e web in te rf a ce c ont ainin g a n i nt e ra ctive ver s i on of t heir ana ly tic approac h to enc ou r a ge rec alc ul ation o f thei r r es ult s whe n up date d o r n e w da ta b ec ame av ailab l e. The autho r s a l s o a cknow ledg e d t ha t th ey d id n ot ha ve ful l a cc ess to the sou r c e dat a for c e r t ain t ria l s , a nd po ten tial err or s in input dat a mig h t ha ve oc curre d in thei r an aly s i s. I n r e s pon se to t he invi ta t i on to t he re s earc h commu nity, w e revi ewed t h e da t a i nclude d in the ir met a- a naly sis and ide n ti fied seve ral incon si ste ncie s and s om e limitation s a s s oc i ate d w ith the dat a re trieval pr oc e ss for the 14 RCT s . In additi on, th ere wer e t ri a ls not i nclude d i n th e i nitial a naly si s, par tially due to da ta not being a vail able i n the public do mai n at the time o f All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprintthis version posted April 5, 2022. ; https://doi.org/10.1101/2022.04.01.22273253doi: medRxiv preprint pu blica t i on , whic h coul d potentially imp rove the ac curac y of th e pooled e stimat e. In thi s ar ticle , we prov ided an upd a ted ve r s i on o f t hi s in s t r ume nt a l variab l e me ta -ana ly si s by p e r f orming sev eral dat a up date s and by ad ding da ta fr o m two addi t i on al R CTs . Ou r up d ate d analy s i s demon st r ate s tha t a redu ctio n in β -amyloi d pl aque is c au sall y an d c on si s t ently a ss ocia te d w ith a s ta tistic ally sign i fican t redu ctio n in c ognitiv e a nd fun c tional d ec line as me a s u red by ch ange s i n the CDR -SB , A l z hei me r ' s Di sea se A sse s sment Sc al e– Cog nitive Su b scale (ADAS -C og ), and MMS E.

F or trial s inc lude d in the initial pu blic a t i o n by Ackle y et al. 1 , t h r e e au tho r s ind e pe nden tly revie wed the s ou rc e da ta for β -am yloid PET S UVR, CD R-S B, A D AS -Co g and MMS E f ro m cli nica ltr ia l s . gov , pu blish ed articl e s an d clini cal s tudy r epo rt s , a nd s u b seque n tly r e s o lved a ny di scr epan cy. In a ddition , on e a u t h or appl ie d t h e same se arch st rategy an d selec t i on c ri t e r ia a s the orig inal pape r 1 t o s eek suppl e ment al trial da ta elig ible to be i ncl uded in thi s upda t e d anal y s i s , e xce pt t ha t trial s w e re fu rt h e r requ ire d to h ave a “ Las t Upda ted Po st ed ” da te at c linic al tr i als .gov b etwe en 3 0 Ap ril 2020 (t h e dat e o f da ta cut o f t h e initi al public ati on) and 1 March 2 022. Updated da t a fr o m the or ig inal ana lysis F o r 1 2 o f t h e 1 4 s t u d i e s f o r w h i c h Ack le y et al . re trieve d t h e da t a en tir ely fr om t h e o r ig inal sou rc e (Cl inica lTr ial s.gov , p e er revie we d public ation s, or othe r publ icly a vail a ble ma te rial s) , w e ide nti fie d an d e l i m i nat e d s e ver a l i n c ons i st e n c ie s be t w ee n t he da t a us ed b y A c k le y et al . a nd th e sou r c e d at a ( Ta ble A1 in t he Appe ndi x 1) . F o r e x a m p l e , t he inpu tte d sta nda rd err o r s (SEs ) f or SUVR and MMS E me asu r e s f rom fou r of th e se tri als w er e inc on s i st ent wi t h t h e data sou rce, incl uding standa rd d e v i a t i o n s ( S D s ) o f t h e S U V R b e i n g u s e d i n p l a c e o f t h e S E s i n t w o t r i a l s ( b a p i n e u z u m a b - 1 [ N CT005 75055 ] and g ant ener umab (Sc a rlet Roa d) [ NCT012241 06 ]) . In addition , da t a for the cha ng e i n CD R- S B and ADA S- Cog in s ol a nezumab 1&2 10 (s o la ne z u m a b- 1 & 2 i n c lu d e d da t a f r o m an i n te g r a ted po pulati on o f mild AD f rom bo th sol a nezumab (E XPED ITIO N ) [ NCT00 905372 ] a nd s o l anezumab (E XPEDIT IO N 2) [ NCT009 04683 ]) w e r e in c o r r e c t l y r e v e rs ed be t w een t h e t r e at m en t a nd p l ace bo g r ou ps. Final ly, the o r i ginal s ourc e data o f aduc an umab-1 (EMERGE ) [ NCT 0248454 7 ] a nd a duca numab -2 (E NG AG E ) [ N CT024 77800 ] t rial s w e r e b a sed on pa r tia l da ta, w hich were u pda te d wit h the la te st da ta from Cli ni calT r ia l s . gov. F or t h e o ther two RCT s, Ack ley e t al . obt aine d a t l ea s t p a rt of t h e d at a t hr o u gh es t im at i n g a lg o r it h ms rath er than di rec tly f rom t h e s ou rce dat a ( T a b l e A 2 i n t h e A p p e n d i x 1 ) . S p e ci f i cal l y , M M S E ch a n g e s i n t he l eca n emab [ NCT01767 311 ] and ve r ube c es ta t- 2 ( APE CS) [ N CT 0195360 1 ] t rial s wer e e s timat e d ba se d on th e cha nge s in th e Alzh ei mer’s D i se a se C ompo sit e Score (AD C O MS) an d C DR- SB, All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprintthis version posted April 5, 2022. ; https://doi.org/10.1101/2022.04.01.22273253doi: medRxiv preprint re spec t i vely . We upd at ed MMSE cha ng e s c o re s u s i ng s ourc e d a t a fr om a c linic al study repo rt f o r l ecan emab a n d a public ati on fo r v eru bece sta t -2 (A PECS ). 11 W e al so id e nti fie d a nd co r rec t e d a n i nconsi s t e ncy i n th e SE valu e s for ve rube ce sta t - 2 (AP ECS ) PET β -amylo id SUVR i n t h e o r i g i n a l pu blica t i on ( Table A 1 in the Appen dix 1 ). Inc lusion of two additiona l RCTs We e xpan de d t h e initi al m e t a -analy s i s b y i ncludi ng two ad d ition al R CT s o f β -amy loid targ eting d r ug s (a ducan umab -3 (P RIME ) [ N CT01 677572 ] and don a nemab (TRA ILBL AZER-ALZ ) [ N CT033 67403 ] ), w i t h da ta o n c hange in PE T β -a myloid SUVR and cli nical outc ome mea sure s a t wee k 5 4 for PRIME and w eek 76 for dona ne mab (TRAIL BLAZE R - A L Z) av aila ble in t he public dom ai n . 12 S t a t istical analy s is A prog r a m i n th e R c ompu tat ion e nv ir o nment ( A p pendix 2) w a s writ t e n b as ed on the s ame me t h odol ogy describ ed in the o r ig inal public ation 1 and r e plica te d the ou tpu t from the public ly a vail able web inte rf ac e. A new progra m wa s written beca use the public ly ava ilabl e w eb inte rfa c e on ly permitt ed the inclu sio n of on e add i t io nal R CT. We compu ted bo th trial - an d drug- speci f i c and po oled e s timat e s of the e f fec t of a reduc tion i n PET β -a myloid SU V R on the cha ng e of CDR -SB , A D AS - Co g, and MMSE t ogeth e r wi t h 9 5% conf id ence i nte r v al s ( CI s) a nd the a s s oc i ated p-va lue s. We u se d the s am e repre s en ta t i o n o f th e e ff ec t e st ima t e s a s in t he o riginal met a- ana ly si s , w here i t w a s de fined a s th e chang e in c linic al en dpoin t s p e r 0 . 1-unit ch ange i n PET β -a myloid SU V R ( a 0.1-uni t reduc ti on in P ET β - a m yl o i d S U VR is a m a t he m at i cal r ep r es en t a t io n t o m e as ur e t h e eff ect of a c o n t in uo us e xposur e wh e r e the c h oic e o f u ni t ch a nge i s dr i ven by c onven ienc e ; i t do e s n ot con fe r to thi s a r bi t r ary unit any act ual cli nical meani ng fulne s s). S olanezuma b-1 &2 (EXPE DITI ON E XT) ( NCT0 1127633 ) w as an ex t en s i on o f s olan ezumab -1&2 with a l onger follow -up p e r i o d f o r c ontinu ed sa fe ty monit oring. In ord er to m axi miz e t he fol low- up p erio d a nd s im ila rly to th e original stu dy, 1 we i nclude d t he d ata fr om sola ne z uma b -1 &2 (EXPE D IT I O N EXT) (ra ther t h an f rom s o lan ezumab -1&2 and sola nezum ab-1 & 2 (EXPE DIT ION E XT)) in a ll p oole d e stimat e s as w ell a s the dr ug -spec ific e s timate for s ola n ez u mab. For A D AS -Co g, the aduc anumab - 3 (PR IME ) trial wa s no t incl uded in the p o oled e stim ate s no r in th e drug -s pecific e st i ma te b ec au s e t h i s e ndpoin t w a s no t mea s u red i n thi s tri al. Final ly, Bexaro ten e (BEAT -AD) [ NCT 01 782742 ] wa s no t i nclude d in the p ooled es timat e f or C DR - SB a s no CDR-S B sou r c e da ta wer e av aila ble. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprintthis version posted April 5, 2022. ; https://doi.org/10.1101/2022.04.01.22273253doi: medRxiv preprint W e p e r f o r m e d s i m i l a r s e n s i t i v i t y a n a l y s e s a s i n A c k l e y et al . 1 by (1) inc ludi ng a l l publish ed da ta, (2 ) on ly inc luding all anti body da ta, an d (3) only incl uding a ll published antib o dy data . Not e t hat l ecan emab w a s the only t rial w ith u npublish ed d a ta i n our ana ly se s , whe rea s in the orig inal ma nuscrip t, bot h lec anem ab and th e two a ducan umab trial s (E MERGE a nd ENGAGE) rel i ed o n un publis hed da ta . W e al so p erf ormed th e foll owing addi tiona l se ns i tiv ity an aly se s: (a ) In clud ed on ly th e mo st r ec en t β -a myloid ta rge t i ng anti bodie s , i. e. g ant ener umab (S ca rle t R oad) , a duca numab (EMER GE, ENGA GE, and PR IME), lec anema b , and donan ema b ( TR AI LBL AZER-ALZ ). (b) Exc luded t he two RCT s evalu a ti ng v erubece s ta t (E PO CH & A PECS ) [ NCT01739348 & NCT01 953601 ] a s ev idenc e of t r ea t m ent - a ssoci a ted c og nitive w o r s enin g 13 du e to t h e inhibi tion o f β - sec re ta se 1 whic h may indic ate of f -t arge t ef fec ts. (c ) Ap pl ied d ata u pdat e s (term ed “ initial trials with data updates ” in Fi g ur e 1 ) a s d e s c r i b e d i n t h e me t h od s withou t inc luding the tw o ne w addition al RCT s d at a s et s (aduc a nu mab-3 ( PRI M E ) and do nanemab (TRAILBL AZER -ALZ ) ) . (d) Ex clud ed t h e leca n emab t rial mon th 12 data t o addr e ss the lim i t a t i on o f no t ac coun t in g for the c orr e la tion be tw ee n da t a fr om we ek 53 (month 1 2) and w e ek 79 (month 18) . (e ) Ex clude d don an emab (TRA IL BLAZER- AL Z) trial dat a, bec au se t he S UVR val ues in thi s t rial wer e c onve r ted f rom th e Cen tilo id sca l e u s in g a n e qua tion . 14 T his s en sitivity an al ysi s wa s p er for m e d t o e liminat e pote ntial in a cc ur a cie s r e sulting from thi s co nver s i on. ( f) E xc l ud e d bo t h l e ca ne m ab t r i al month 12 and d ona nema b (T RA I LBLAZ ER -ALZ) t rial da ta fo r re a son s spec i fied i n (d) a nd (e ).

F or the pool e d e stima te s o n “ All Data , ” t hi s updat ed meta -a n alysi s showe d st ati s tic ally s igni fican t e videnc e o f a cau s al r e l ation shi p be t we en th e r educ ti on in b r a in β - a m y l o i d p l a q u e l e v e l s a n d redu ctio n in cog nitive and func ti onal de c line a s m ea sure d b y CDR-S B (0. 09 p oin t p e r ea ch 0 .1-uni t redu ctio n in PET β - a m y l o i d S U V R ; 9 5 % C I : 0 . 0 3 4 , 0 . 1 5 ; w i t h a p - v a l u e o f 0 . 0 0 1 6 ) ( Fi gu r e 1A ). T he up date d poin t e st i m ate is a ppro ximatel y 1.5 time s t he o r i ginal e stimat e (0 .0 58 with 95% CI: -0 .031, 0 .15) (Tab l e 1 ). 1 Multipl e sen sit ivity ana lyse s we re per fo rmed t o ex clude the i nfluen c e of sp ec ifi c trial s a f fec te d by inh e r e n t l imit ation s a s des c ribed in th e Me thod s . The se s en siti vity a nalys es ( Figu re 1 A a nd Fig ur e A 2 in the Appendix 3 ) yiel ded similar poi n t e stima te s for C DR -SB, w it h p-valu e s < 0.05 , e xce pt fo r “ initial trials with data updates .” All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprintthis version posted April 5, 2022. ; https://doi.org/10.1101/2022.04.01.22273253doi: medRxiv preprint Ta b l e 1 . Compari so n of t he ma in r esul ts betw ee n the o rig inal a nd upd ate d analy sis on th e e ffe ct o f a redu ctio n in β-a myloi d SUV R on c hange i n cog nitive endpoin t s. P o sitive v alue s o f the e ffe ct e stimat e— for e ac h 0.1 -uni t r edu ctio n in PET S U VR—i ndic at e tha t β -amy loid red u c tion sl ows c ognitiv e dec line . ADAS - Cog , Alz he im er’s D i se a se A s s e ss ment Sc al e– Co gnitive Sub scal e; C DR- S B, Cli nical Deme ntia Ra t i ng–Su m o f Boxe s; CI , c onfid enc e i nterva l ; MMSE, Mini -M ent al Sta te Ex a mination ; N A, n ot av a i la b l e . T he updated me ta- analy s i s fur ther s h ow ed a sta ti st i call y signi fic an t ca usa l ef fect o f β -amy loid redu ctio n on reductio n in c ognitiv e dec line as mea su red by ADAS - Cog (0.33 poi n t per ea ch 0.1 -uni t redu ctio n in PET β -amyl oid SUVR ; 95 % CI: 0 .12, 0.55 ; w ith a p -v alue o f 0.0025 ) ( Fig ur e 1B ), w hich r e m ai n e d t he cas e in a l l se ns i t i v i t y ana l y s es pe rf or me d ( Fi g ur e 1 B and Fi g ur e A 2 in the Appendix 3 ) e xce pt f or “initial trials with data updates.” W e w ere n ot abl e to co mp are t he upda ted po oled e s t i m a t e w i t h t h e o r i g i n a l e s t i m a t e f o r A D A S - C o g a s t h i s w a s n o t p r o v i d e d i n t h e o r i g i n a l w o r k f r o m Ac kley et al. 1 T he upd a ted met a- an alys is al so s howe d a stati s t i cal ly signi fica nt c au sal re la ti onship be tw een β - a myloid reduc t i on an d r educ ed de clin e as me a s u r e d by the M MS E (0.1 3 poi n t per e ach 0.1 -unit redu ctio n in PE T β -amy loid SUVR; 95 % CI : 0.0 17, 0 .24; w ith a p-va lu e of 0.02 4) ( Fig ur e 1C ). T h e po oled e s tima t e i n th e upd ated ana ly si s wa s fou r time s th e orig in al e s t i mat e (0 .034 with 95% CI : − 0.056, 0.12) ( Ta b l e 1 ). 1 W h e n we p erf or me d only dat a upda te s a s de scri bed in the Meth od s w ithout i ncludi ng t h e tw o ne w addi tion a l RCT s da ta se t s (a duc anumab -3 [PR IM E] and do na nema b [TR A I LBLAZ ER -ALZ] ) , the up da ted met a -ana ly si s als o d emon strat ed a sub s t an tial s hi ft f rom the orig inal re s ul t s on the MMS E en dp oint (0.10 poin t pe r ea ch 0 .1- unit r edu cti o n i n PE T β -amy loid S U VR; 95% C I: − 0.023 , 0.23 ), a l though th is w a s n ot s t ati sti call y signi fic ant . F inall y, a s e n s i tiv ity ana lysi s incl uding only the most r ec en t β - a m y l o i d t a r g e t i n g a n t i b o d i e s ( i . e . g anten erumab, a duc anumab, l ec anema b , and donan ema b) , s howed over all n umeric ally stronge r e ffe ct s a cro ss all thr ee en dpoi nt s : C DR- S B (0.0 95 point per eac h 0 .1- unit reduc ti on in PET β -amy loid C ognitive en dpoi nt s Original analysi s (“All data” ) U pdated analysis (“All data”) Eff ec t ( 95% CI) Effect (95% CI) P-V a lu e CDR - S B 0 .058 ( − 0 .031, 0. 15 ) 0.09 (0.0 34, 0.1 5 ) 0. 0016 AD AS -Co g NA 0.33 (0 .12, 0.5 5 ) 0. 0025 MMSE 0 .034 ( − 0 .056, 0. 12 ) 0.13 (0.0 17, 0.2 4 ) 0 .024 All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprintthis version posted April 5, 2022. ; https://doi.org/10.1101/2022.04.01.22273253doi: medRxiv preprint S U VR; 95% C I : 0.039 , 0.15; with a p-v alu e o f 0.0 008 ), AD AS- Cog (0 .41 poi nt p er eac h 0.1 -uni t redu ctio n in PE T β -amyl oid SUV R; 95% C I: 0.2 , 0.61 ; w it h a p -val ue o f 0.00 01 ), a n d MMSE (0.16 p oint pe r ea ch 0.1 -uni t reduct ion in PE T β -a myloid S U VR; 95% CI: 0. 054 , 0.27; wi t h a p-va lue of 0 .0032) w ith con s i s tent stati s tica l s i gnific anc e ( Fi gure 1). T r i al- a nd d r ug -spec i fic e s tima t e s for C D R-SB, AD AS -Cog, and MM SE are pre se nte d in Fi g u r e A 1 in the Appendix 3. T he RCTs inc luded in thi s up dated a nalysi s a re summariz ed in Appendi x 4 .

I n t h i s s tudy, w e up dat ed a previou sly p ublish ed in st r u men tal va r i able me t a - a n a lysis 1 o f t h e ef fe c t of a redu ctio n in β -amyloi d pl aque as mea sure d b y PET on cha nge in cog nitive dec line, by c orr e ctin g a nd improvi ng t he o rigi nal d a t a input s a nd inc rea sing the num be r o f R CTs incl ud ed. In c on tra st t o th e i nitial an aly s i s, our study d emon st r at es that a r e duc tion in β - a m y l o i d i s c a u s a l l y a n d c o n s i s t e n t l y a ssoci a ted with a stati s tical ly signi fic ant reduc t i o n in c ognitive and func t i onal d e cline as me a sured b y c hang es in CDR -SB , AD AS -Cog, a nd MMS E. S t reng t hs and l imitat i ons A unique stre ngth o f t he me thodol og y de velope d in t h e origin a l publi ca tion 1 is t h e us e of t he i ns t rumen tal va r i able appro ac h t o ad dre ss th e i ssue of pot enti al c on foun ding bia s f ound i n c orr e la tion anal y s i s. I n addi tion, the int egratio n o f da ta from m ul tiple tr ia l s s u bs t an t i a lly improve s st ati stic al p r ec i sion r ela tiv e to any indiv i dual trial . De spit e be ing c atego rized a s l evel 1 ev idenc e wi t h multiple adva ntag es , met a-a n alys es a re no t w ithout l imi tati on s, 15 s om e o f whi ch h ave alr ea dy be en highli gh ted in th e o ri gina l p ublica ti on. 1 16 Addi t i on al poi nts o f c aut ion in int erpre t a t i on s h ould be e mpha siz e d . F irst, subjec t s i nclude d in thi s me t a - a nalysi s ar e a t di ff eren t s t a ge s o f A D, from mild cog nitive i mpairment d ue t o A D to mod era te st age o f A D demen tia . In a d dition , β - a m y lo i d p os it iv i t y (me a s ur ed w ith visu al scal e or P ET SU V R t h r e shol d) w a s not a p rer equi sit e inc lusion cri teri on in th e ma jority of i nc luded s tudie s (9 o f 16 st udie s ). I t i s bi ol ogic ally plau sible tha t subjec t s i n t h i s he t e r og en eou s p opula t i on may d erive d i ffe r e n t l evel s o f b e ne fi t in c ognitive func tion from β -amy loid redu ctio n. In thi s c on text, comb ining t hose indiv idual s with p r od r om a l, mi ld, o r moder at e AD, in w hich the und er l ying pa t h o logy ( β -amy l oid loa d a nd downs tre am proce s s e s) may v ary, co uld caus e di ff i cul ty in inte rpre ting th e re sul ts. 16 All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprintthis version posted April 5, 2022. ; https://doi.org/10.1101/2022.04.01.22273253doi: medRxiv preprint S e c o n d , w h i l e w e a s s u m e a l i n e a r i t y b e t w e e n β -am yloid depo si tion and c ogn itiv e a nd func tiona l de clin e, the pr eci s e t empor al and spa ti al dynam ic of thi s r el a tion s h ip i s no t w ell under stood . For e xampl e, a lt hough a chang e i n SU VR may be a g ene ralizabl e met ric, it m ay not op tima lly re flec t spa tia lly and t emporally h ete r o gen ou s prope rtie s of th e und erly ing pa tholog y assoc ia ted with a nd r e l e v a n t t o A D a n d i t s c l i n i c a l m a n i f e s t a t i o n s , p a r t i c u l a r l y a t t h e e a r l y s t a g e o f t h e d i s e a s e . A s s u c h , rec en t finding s u sing r e gion al SUV R data ha ve de mon s tr at ed promi se . 17 18 T hird, t he in s trum ent al v ariable an aly si s requ i r e s the ab s ence o f o ff - targe t eff ect s from the ther ap eu tic a gent s. In ou r pre s e n t stu dy , w e partial ly a ddre ssed t h i s limit ati on b y pe r forming a sen si tivity ana ly sis incl udi ng only tr ia l s with antibody th erapi e s tha t, due to their spec i ficity an d di r e ct impac t on β -amylo id, may pr ov ide more a ccu r a t e e s tima te s o f t his r e la tion ship . Howev er , thi s w ould not have ad dr e sse d t h e h ighly c omplex temp or a l rel ati on s h ip tha t lik ely ex ists betwe en th e i mpact of a myloid pl aque remo val a nd t he dec line i n cog ni t i on and func ti on th at is inhe ren tly limited b y t h e s h o r t - t e r m s e t t i n g o f m o s t t y p i c a l c l i n i c a l t r i a l s a n d w h e r e a p o t e n t i a l l y d e l a y e d - o n s e t e f f e c t c annot be cap tur ed. F ourt h , th e v ariou s r adiot race rs u sed i n trial s inc lud ed in thi s an aly si s di ff er in their s en s i t i vity , spec i fici t y , va ria bili ty, d ynamic rang e s, an d o the r pe rfo r ma nce me t r ic s 19-23 . The r e for e, al though di ffe re nt a myloid trac er s produc e highl y con s i s ten t an d hig hly c orrela t e d r e s ul t s, SUVR de rived from di ffe re nt t rac e r s are no t equi val en t a nd sh ould b e co mp ared or c ombin ed w ith som e c auti on. F urt he r more , al thoug h a myloid PET ha s been s how n to be robu st agai n st di f fe r e nt qua n t ifi c atio n me t h od s 24 , dif fe ren t an aly si s pipeli n es m ay a ls o have re sult ed i n s m a ll dif fe renc e s betwee n studie s . F inall y, th e a ss e ss m ent o f chang e in A D -rel at ed impa i r m ent o f co gni tion and fu nction a t the ea rly ph ase s o f AD i s no t fully a dd r e ssed by t he c linic al sco re s u til iz e d i n t he se c linic a l tr i al s , in par t i cula r the MM SE , due to i ts l imited se n s itiv ity to cap ture p rogre s s i on in cog nitive d e cli ne . Thi s wa s fu r th er em p h as i z ed i n ou r c ur r e nt st u d y b y t he d e m o ns t ra t i o n of h ig he r p- v a l ues fo r MM S E c o mp a re d w i t h CDR -SB a nd AD AS -Cog e n dpoint s (Figu re 1) . Im plications T hat a st ati s tic ally s ig ni fica nt cau sal a sso cia t i on be twee n dec rea s ing PET -mea s ur ed β -am yloid p laqu e a nd r eduction o f c ogni tiv e and f unc tion a l dec line wa s con si ste nt l y demon st r a te d on all thr ee c linic al All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprintthis version posted April 5, 2022. ; https://doi.org/10.1101/2022.04.01.22273253doi: medRxiv preprint e ndpoin ts d e s pit e som e of the a for eme nt i oned limi t a t i o n s hig hlight s the po ten t ial of β -amy loid as a v iable bio logic al t a r g et in A D. A s more data ac cumu la te i n th e fu ture , w e hop e t ha t som e of the l imitation s can b e addr e s s e d by a naly si s of da ta w ith longe r fo ll ow-up p eriod s . In a ddition , the a bility to harmo nize the d ata on β -a myloid lo a d by us i ng Cen tiloid s will fur ther a cco u nt f or t he di f fer ent prope rtie s o f β - a m y l o i d r a d i o t r a c e r s . T h e s e e f f o r t s w i l l s h e d m o r e l i g h t o n t h e e f f e c t o f β -amy loid redu ctio n on c ognitiv e and f u nctio nal decli ne and guide futu re dr ug devel o pment a nd c linic al a pplic ation s.

T his upda ted i ns tr u m ental va r i able m e t a - a naly si s, whi ch i s ba s ed on 16 r andomiz ed c linic al tr ial s an d e xpands on the o rig inal w or k by Ack ley et al ., 1 d e m on st r a t ed a c o ns ist e n t a n d st at is t i ca l l y s i g nif i c a n t i mpact of PET β -amyloi d S U VR ch ange on thr e e commonly u s ed c linic al outco me mea s u re s. Mo r e da ta a nd re s earc h a re need e d to fu rt h e r cha r a ct eriz e the pr eci se sp atial /t em poral prop ert i e s and po t e n t i al he ter oge nei ty of the c au sa tive rel ati on s h ip betw ee n β -amylo id cl earanc e and c ognitiv e and func tio nal t r aje ctory w it h in the A D con t i nu um. PATI EN T A N D P UB L IC INV O L V E M E N T: P ati ent s o r the public we re no t i nvolv ed in the de sign, o r c onduct, o r repo rting, o r dissemina t i on pl ans o f thi s re sea rc h. ACKNOWL EDGMEN TS: We would l ike to tha nk Ta mmy Jian g for quali t y -ch ec king t h e inpu t da t a ; Joh n O’G orman, S ama nth a Bu dd Haeb erlein , Tuck er War d, Kathl ee n Gr obb e n, Anni e Racine an d P r iy a Si nghal f o r r ev iewi ng the ma nuscrip t and pr ov iding h elpful c omme nts . COM PETIN G INT ERESTS : Ch angyu Sh en, Menglan P ang, Ling Zh u, Aud rey Gabel le , Ar i e Ga fson, Ivana Rubino, Shib es hih Be lach ew an d Ca rl de Moor a re emp loye es and sha rehol d ers of Bi og en inc . Jim E. Galv in MD, MPH i s a P rof e ss or of Neu r o logy a t Unive rsi ty of Mi a mi, con sul tan t f or Bio gen, Alpha Cogn ition , Ei sai, and Co gnivue , and h a s re s earch f u nding f ro m NIH, and c linic al inc om e f rom pati e nt c are. R obe rt W . Pla t t , P hD, ha s an ong oing c on s u lting a rrange ment with Bi ogen . FU ND I N G : T his work w as funde d by Biogen . RE FERENCES: All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprintthis version posted April 5, 2022. ; https://doi.org/10.1101/2022.04.01.22273253doi: medRxiv preprint 1. Ack le y SF , Zimmerman SC, Br enowitz W D, e t al. Ef fect of reduc t ions in amyloid levels on c ognit iv e change in randomized tr ials : instrumental var iable me ta-analysis . Bmj 2021;37 2:n156 . doi: 10.113 6/bmj.n1 56 [publis hed Online First: 2021 /02/ 2 7] 2. Karran E, Merc k en M, De Str ooper B. The amyloid ca scade hypothes i s f or Alzheime r's dis ease: an apprai s al fo r the deve lop ment of ther apeu tics . Nat Rev Dr ug Disc ov 2011;10(9): 698 -712. doi: 10 .103 8/nr d3505 [pu blished Online Fir s t : 20 11/08/20] 3. Mc Khann G M , Knopman DS, Chertkow H, e t al. The diagnosi s of dement ia due to Alz heimer's diseas e: r e c ommendatio n s fr om the National Institute on Agin g- Alz heimer's As socia t ion workgroups on diagnostic guidelin e s for Alz heime r's disease. Alz heimer s D em ent 2011;7(3) :2 63-9. doi: 10.1016/j .jalz .2 011. 03.00 5 [publis hed O nline First: 2011/04/26] 4. Jack CR, J r., Knopma n DS , Jagus t WJ, et a l. Hypothetic al model o f dynamic biomar kers of the Alzheimer's pathological c a s c ade. Lancet Ne ur ol 2010;9(1): 11 9-28. doi: 10.1016 /s147 4-4422( 09)70 299-6 [pu blished Online Fir s t : 2010 / 01 /20] 5. Karran E, De St rooper B. The amyloid hy pothesis in Alzheimer diseas e: n ew insight s f rom new t herapeut ic s. N a t Rev Drug D iscov 2022 doi: 10.1 038/ s41573-0 22 -003 91-w [published O nline First: 2022/0 2/19] 6. Thal DR, Rüb U, O r antes M, et al. Phas e s of A bet a-d eposition in the human brain and its relevanc e fo r th e development of AD. N eur ology 200 2;5 8(12):179 1- 800. do i: 10.1212 / wnl.58 .12.1 791 [ publis hed Online First: 2002 /06/27] 7. Ingels son M, Fukumoto H, Ne well KL, et al. Early Abeta accumulation and pr ogressive synaptic los s, glios i s, and tan gle for m ation in AD brain. Neurology 2004;62(6):9 25-31. doi: 10.1212/01 .w nl.0 000 11 5115 .989 60.37 [published On line Fir s t: 20 0 4/ 0 3/24] 8. G oate A, Chartier -Ha r lin MC, Mulla n M, et al. S egr egation of a miss ense mutat ion in the amyloid precursor pr otein gene with familia l A lzheimer's dis ea se. Natu re 1991;34 9(6311): 7 04-6. doi: 10.1 038/ 349704a 0 [publis hed O nline First: 19 91/02/21 ] 9. Karlawis h J, Grill JD. T he approval o f Aduhe lm r is ks eroding public tr us t i n Alz heimer resea r ch and the FDA. Nat R e v Neurol 2021;17(9) : 523-24. doi: 10. 1038/ s41 582- 021- 00540-6 [published Online F ir s t : 20 21 / 07/17] 10. S ieme r s ER, Sundell KL, Carlson C, et al. Phase 3 solanezumab tr ials: Secon dary outcomes in mild Alz heimer's disea s e pat ien ts. A l zh e i m e r s D em en t 2016;12(2) : 110-2 0. doi: 10.1016 / j.jalz .2015 .06.1 893 [publishe d Onlin e Fir s t : 2 015 / 08/0 5] 11. E g an MF, Kos t J, Vos s T , et al. Randomized Trial of Ver ub eces t at for Pr odromal Alz heimer's Dis ease. N Engl J M ed 2 019;380(15): 1408- 20. doi: 10.1056 /NEJMoa181 2840 [published O nline First: 2019 /04/ 11] 12. S evigny J, Chiao P, Bus sièr e T, et a l. The an t ibody aduca numab reduce s Aβ plaqu es in Alz heimer's diseas e. Natur e 2016 ;537 (7618):5 0-6. doi: 10.1 038/nature193 23 [published O nline First: 2016/0 9/02] 13. W e s s els AM, Lines C, St ern RA, et al. Cognitive outcomes in t rials of two BACE inhibit o rs in Alz heime r 's diseas e. A l zheimer s De ment 2020;16(11): 148 3-92. doi: 10.1002 / alz. 12164 [published Onlin e Fir s t: 20 20 / 10/ 14] 14. N avitsk y M , Joshi AD, Kennedy I , et al. Standar diz ation of amyloid qua ntitation wit h florbe t apir s t andardized uptake value ratios to the Cent iloid s cale. Alzheimers Dement 2018 ;14(1 2):1565- 71 . doi: 10 .1016/ j .jalz.2 018.0 6.135 3 [published Onlin e F ir s t : 2018 / 07/ 15] 15. E ysenc k HJ. Me t a-analys i s and its pr oblems. Bmj 1994;30 9(6957) :7 89-9 2. doi: 10.1136 / bmj.309 .6957 .789 [publishe d O nlin e First: 199 4 / 09/2 4] All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprintthis version posted April 5, 2022. ; https://doi.org/10.1101/2022.04.01.22273253doi: medRxiv preprint 16. Mangiala sche F, S olomon A, Winblad B, et al. Alz heimer's disease : clinic al t rials and dr ug dev elopment. Lancet N eur ol 2010;9(7 ):702- 16. doi: 10.10 16/s14 74-4422( 1 0)70119-8 [published O nline First: 2010/0 7/09] 17. F ar rell ME, Chen X, Rundle MM, e t a l. Regional amyloid acc umulation a nd cognitive dec line in initially amyloid-negativ e a dults. Neur ology 201 8;91(19):e18 09- e21 . d oi: 10.1212 / wnl.00 00000 000 0 06469 [publis hed O nline First: 2018 /10/12 ] 18. G r othe MJ , Barthel H, S epulc r e J, et al. In vivo staging of regional amylo id deposition. N eur ology 2017; 8 9(20):20 31-38. d oi: 10.1212 / wnl.00 00000 0000 04 643 [pu blis h e d O nline First: 2017/10/20] 19. Yeo JM, Waddell B, Khan Z, et al. A s y stematic review and meta-analysis of 18F-labeled amyloid ima ging in Alzheime r's dise as e. Alzheimers Dem ent. D iagn. As s e s s . Dis. Monit. 2015; 1(1):5-13. doi: ht tps:/ /doi.or g /10.101 6/j.dadm.2 014.1 1.004 [ publis hed O nline First: 2015/03/01] 20. L andau SM, Thomas BA, Thurfjell L, et al. Amyloid PET imaging in Alz heimer ’s disea s e: a c o mp a r is o n o f th re e ra d i o tra c e rs . Eur . J . N ucl. Med. M ol . Im aging . 2014;41 (7):139 8- 407. doi: http s :// dx .doi.or g/ 10. 1007 %2F s00 259-014-275 3 -3 [published Online First: 2014/0 3/20] 21. Krishnada s N, Villemagne VL, Doré V, e t al. Advanc es in Brain Amyloid Imag ing. Semin. N ucl. Med. 20 21;51( 3): 2 41–252. doi: 10.1053 /j. s emnu c lmed.20 20 .12. 005 [published O nline First: 2021/01/19] 22. Cho SH, Choe Y S, Kim YJ, et al. He ad-to- head c ompar ison of 18F-flor be t aben and 18F- flutem et amo l in the cortical and s t riatal regions. J. Alzheimers Di s . 20 20;76 (1):281 -90. doi: 10.3233/ J AD-200079 [published O nlin e Fir s t: 202 0 / 06/ 30] 23. W olk DA, Z ha n g Z , Boudhar S, et al. Amyloid imaging in Alz heimer 's diseas e: compar is on of flo rbetapir and Pitt s burgh compound- B pos it ron e mission tomogr a phy. J . N eur ol. N eur o s ur g. P s y chiatry . 2012;83( 9): 92 3-6. doi: 10.1136/ jnnp-2012 -3025 48 [published O nline First: 2012/07/11] 24. L andau SM, Breault C, J os hi AD, et al. Amyloid -β imaging with Pit tsburg h compound B and florbe t apir: comparing r a diot racers and quantif ication meth ods. J. Nuc l . M e d. 2013;54(1): 70- 7. doi: 10.29 67/ jn ume d.112.10 9009 [pub lished Online F ir s t : 2012/1 1/19] All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprintthis version posted April 5, 2022. ; https://doi.org/10.1101/2022.04.01.22273253doi: medRxiv preprint Figure 1 All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprintthis version posted April 5, 2022. ; https://doi.org/10.1101/2022.04.01.22273253doi: medRxiv preprint Figure Legend Fi g u r e 1. Fore st pl ot s of t he poo le d e stima te s r epre s enting the e ff ec t o f a d ec r e a se in br a in β - a myloid as me asured b y PET on cha ng e in A) C DR-S B, B) ADAS - Cog , and C) M MS E. P o s itiv e val u e s of the e f fect e s tima t e — f or e ach 0.1 -unit redu ctio n i n PET SU VR —indic at e t hat β -a myloid r e duction redu ce s cog ni tive decl in e. Cen t er a nd wi dt h of dia mond s re pres ent poo le d es timat e s and 95% c onfidenc e in terva l s , r e spectiv ely. T he tria l o f l eca nemab i s unp ubl i s he d and wa s ex clude d from th e “ All published data” a nd “ All published antibody data ” c at egorie s i n the sen s i t i v ity anal ys e s. Mo s t rec en t β -amy loid t arge ting antibod i e s i nclu ded ga nte neruma b, a duca numa b ( ENGA G E , EMERGE, P RIME ), leca n emab, a nd don anema b t rial s . A DAS - Cog, Alzh eime r ’s Di se a s e As se ssm ent Sc ale – Co gnitive S ub s c al e; C DR -SB, Cl inica l D e mentia Ra ting– Sum o f Boxe s; CI, con fi d ence i nte r v al; MMSE , M i ni - M en t al S t at e Ex a m in a t i o n. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprintthis version posted April 5, 2022. ; https://doi.org/10.1101/2022.04.01.22273253doi: medRxiv preprint