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Ame ican Jou nal o Medical Gene ics Pa C: Semina s in Medical Gene ics, 2025; 0:e32127
h ps://doi.o g/10.1002/ajmg.c.32127
Ame ican Jou nal o Medical Gene ics Pa C:
Semina s in Medical Gene ics
REVIEW ARTICLE OPEN ACCESS
Genomics Re iew o Selec i e RET Inhibi o s Sensi i i y in
Thy oid Cance Clinical T ials
Sa aGil- Be nabé1,2 | LucíaGa cía- DeLaFuen e1 | Alejand oGa cía- Ál a ez3 | GinesaGa cía- Ros án1,2 | JaumeCapde ila3 |
Jo geHe nando3
1Pa hology Depa men , Facul y o Medicine, Valladolid Uni e si y, Valladoli, Spain | 2G oup Pa hobiology o Cance : In e - , In a- Tumo He e ogenei y
and Molecula Ta ge s, Ins i u e o Molecula Gene ics and Biomedicine (IBGM), Valladoli, Spain | 3Gas oin es inal and Endoc ine Tumo Uni , Medical
Oncology Depa men , Vall d'Heb on Uni e si y Hospi al, Vall d'Heb on Ins i u e o Oncology, Ba celona, Spain
Co espondence: Sa a Gil- Be nabé (sa a.gil@u a.es)
Recei ed: 4 Sep embe 2024 | Re ised: 5 Decembe 2024 | Accep ed: 16 Decembe 2024
Funding: The au ho s ecei ed no speci ic unding o his wo k.
Keywo ds: medulla y hy oid cance | oncogenes| papilla y hy oid cance | P alse inib| Selpe ca inib| a ge ed he apy| hy oid gland
ABSTRACT
RET gene is a d i e o hy oid cance (TC) umo igenesis. The incidence o TC has inc eased wo ldwide in he las ew dec-
ades, bo h in medulla y and ollicula - de i ed sub ypes. Se e al d ugs, including mul ikinase and selec i e inhibi o s, ha e
been explo ed. Selpe ca inib and p alse inib a e selec i e RET inhibi o s ha ha e shown clea clinical bene i s o pa ien s in
he LIBRETTO and ARROW ials, espec i ely. Cu en ly, hei de elopmen and applica ion in clinical p ac ice a e ongoing.
Howe e , i s e icacy in di e en RET pa hogenic a ian s has no ye been well es ablished. Al hough selpe ca inib and p al-
se inib achie ed a high ORR, no da a a e a ailable ega ding he di e ences in umo esponses o bo h TC g oups acco ding
o RET pa hogenic a ian s. Clinical ials and li e a u e ha e analyzed he e icacy o selec i e RET inhibi o s wi h a special
in e es in he mos common a ian s. A e iew o LIBRETTO and ARROW ials was made ega ding he change in umo
size depending on he pa hogenic a ian s. M918T pa hogenic a ian esul ed in a highe comple e esponse a e. Pa ien s who
unde wen usion had he highes ORR (objec i e esponse a e). MKi- ea ed pa ien s did no exhibi signi ican di e ences
om un ea ed pa ien s. Di e en RET pa hogenic a ian s a e no bioma ke s o RETi esponse in TC. Selpe ca inib showed a
endency o achie e a comple e esponse. All pa ien s wi h RET pa hogenic a ian s should ecei e ea men wi h selpe ca inib
o p alse inib a any momen o he he apeu ic schedule owing o o - a ge inhibi ion and oxici y. The e o e, new a ge s o
d ug sensi i i y and esis ance should be explo ed.
1 | In oduc ion
1.1 | Thy oid Cance s
Thy oid cance (TC) is he mos p e alen malignan neoplasm
o he endoc ine sys em and i s incidence has inc eased o e
he las decades (Cabanillas, McFadden, and Du an e 2016).
Howe e , ad ances in he iden i ica ion o gene ic bioma k-
e s and he de elopmen o a ge ed d ug he apies a e being
made. Howe e , agg essi e TC mo ali y has no dec eased.
Radioac i e iodine ea men a e su ge y imp o es he o e all
su i al o di e en ia ed hy oid cance (DTC) pa ien s wi h a
high isk o ecu ence (Boucai, Za e eo, and Cabanillas2024).
Ne e heless, i ually all pa ien s wi h me as asis e en ually
p og ess a e sys emic ea men .
Depending on hei cellula o igin, TC can be classi ied as ollic-
ula and C cell- de i ed cance s. Follicula - de i ed umo s we e
u he classi ied acco ding o hei his ological deg ee o dedi -
e en ia ion. Follicula cell- de i ed (FC- TC) malignancies include
This is an open access a icle unde he e ms o he C ea i e Commons A ibu ion-NonComme cial-NoDe i s License, which pe mi s use and dis ibu ion in any medium, p o ided he o iginal
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© 2025 The Au ho (s). Ame ican Jou nal o Medical Gene ics Pa C: Semina s in Medical Gene ics published by Wiley Pe iodicals LLC.
2 o 11 Ame ican Jou nal o Medical Gene ics Pa C: Semina s in Medical Gene ics, 2025
di e en ia ed (DTCs), poo ly di e en ia ed (PDTC), and anaplas-
ic hy oid ca cinomas (ATCs) (Juhlin, Me e, and Baloch 2023)
(Table1). The mos common d i e o he disease is he BRAFV600E
pa hogenic a ian . O he d i e s ha e been epo ed o ha bo
pa hogenic a ian s in he RAS iso o ms and RET ea angemen s.
In ecen yea s, he su i al a e o DTCs has no ably imp o ed be-
cause o he use o mul ikinase inhibi o s (MKi) (Boucai, Za e eo,
and Cabanillas2024; Fagin, K ishnamoo hy, and Landa2023).
Medulla y hy oid ca cinoma (MTC) a ises om C cells, wi h
25% o cases being ela ed o amilial o he edi a y synd omes.
RET pa hogenic a ian s a e he main d i e o his neoplasm,
ollowed by RAS. The su i al a e o hese umo s in 5 yea s
is 65% (S ama akos e al.2011). MKis has esul ed in an imp es-
si e imp o emen in he su i al o hese pa ien s (Ca ling and
Udelsman2014).
1.2 | REa anged Du ing T ans ec ion
In 1985, a new oncogene, RET (REa anged du ing
T ans ec ion), was disco e ed. RET is loca ed on ch omo-
some 10 (10q.11.2), and he encoded p o ein is a ansmem-
b ane y osine kinase ecep o (RTK) (Takahashi, Ri z, and
Coope 1985; Sal a o e, San o o, and Schlumbe ge 2021),
p edominan ly ound in pa a ollicula hy oid C cells. RET
p o ein is no cons i u i ely exp essed in ollicula cells com-
pa ed wi h pa a ollicula cells.
RET ecep o ac i a ion in ol es he binding o he glial cell-
de i ed neu o ophic g ow h ac o (GDNF) amily o ligands
o a glycosylphospha idylinosi ol- linked co- ecep o on he cell
su ace, called he GDNF ecep o (GFRα). As a esul o he in-
e ac ion be ween RET kinase and he GDNF amily o ligands,
he ecep o dime izes, leading o he phospho yla ion o speci ic
y osine esidues wi hin he ecep o y osine kinase domain,
which in u n p omo es ecep o ac i a ion (Goodman e al.2014).
Consequen ly, ac i a ing RTK and RET igge s downs eam pa h-
ways ha p omo e cell g ow h, p oli e a ion, su i al, and di e -
en ia ion, including he MAPK and PI3K signaling pa hways.
Upon homodime iza ion o RET kinase, i s in acellula do-
main unde goes phospho yla ion a se e al y osine esidues
ha a e in ol ed in signal ansduc ion and ac i a ion o
downs eam kinases (Figu e1A). Nume ous pa hogenic a i-
an s in RET, including poin mu a ions and ea angemen s,
ha e been shown o igge cons i u i e ligand- independen
oncogenic ac i a ion (Goodman e al.2014; Regua, Najja , and
Lo2022). Poin mu a ions a e a ea u e o MTCs, pa icula ly
in codons 634, 804, and 918. In con as , oncogenic ac i a ion
TABLE 1 | Incidence and p e alence o di e en al e a ions in hy oid cance (San Román Gil e al.2020; Hu e al.2021; Ib ahimpasic e al.2019;
S ama akos e al.2011).
Classi ica ion o
hy oid umo s
Thy oid
cell o igin Incidence Mu a ons 5-yea
su i al
DTC
Di e ena ed
Thy oid
Cance
PTC
Papilla y
Thy oid
Ca cinoma
FC
Follicula
cells
80%
RET ea angemen s
BRAF
RAS
98%
FTC
Follicula
Thy oid
Ca cinoma
10% RAS 95%
PDTC
Poo ly Di e en a ed Thy oid
Ca cinoma
2-15%
RET ea angemen s
66%
ATC
Anaplas c Thy oid Ca cinoma 1%
RET ea angemen s
12%
MTC
Medulla y Thy oid Ca cinoma C cells 2-3% RET mu a ons 65%
BRAF
RA
S
EIF1AX
TERT
TP53
TERT
BRAF
RA
S
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o RET in DTCs is achie ed ia usion wi h gene pa ne s
such as CCDC6, NCOA4, and KIF5B (Sal a o e, San o o, and
Schlumbe ge 2021).
1.3 | RET Genomics in Thy oid Cance
RET pa hogenic a ian s a e classi ied as poin mu a ions (he-
edi a y o spo adic), p ope MTC disease, o ea angemen s
p esen in FC- TC (Figu e1).
1.3.1 | He edi a y RET Poin Mu a ions
Poin mu a ions a e he mos common ge mline RET pa hogenic
a ian s. Di e en ypes o synd omes can a ise depending on
he RET pa hogenic a ian de ec ed.
MEN (Mul iple Endoc ine Neoplasia) 2 ge mline RET pa hogenic
a ian s esul in gain- o - unc ion mu a ions, in con as o o he
he edi a y p edisposi ions o cance synd omes caused by loss-
o - unc ion pa hogenic ge mline a ian s (San o o e al.1995).
MEN2A is he mos common he edi a y ype o MTCs.
Pa hogenic a ian s in he 634 codon o RET exon 11 ha e been
obse ed in mos MEN2A cases. O he al e a ions ha e been e-
po ed in codons 609, 611, 618, and 620 in exon 10 (Ma hiesen
e al. 2022). All o hese pa hogenic a ian s a e in he RET
exon ha codi ied he ex acellula domain and a e en iched
wi h cys eine esidues (Figu e 1B). MEN2A pa ien s usually
de elop MTC, pheoch omocy oma, and hype pa a hy oidism.
Cu aneous lichen amyloidosis is liga ed o a ian s o codon 634
and Hi schsp ung's disease wi h al e a ions in he o he a o e-
men ioned ex acellula egions.
Rega ding MEN2B synd ome, he mos common pa hogenic
a ian is M918T, ollowed by A883F (Ma hiesen e al.2017).
The clinical mani es a ions o MEN2B include MTC, pheo-
ch omocy oma, and ex a- endoc ine ac o s, including
ganglioneu oma osis o he ae odiges i e ac (Ma hiesen
e al.2022).
In pa ien s wi h Familial MTC (FMTC) synd ome, he mos
p e alen al e a ions a e loca ed in codons 533, 768, and 804
in he ex acellula and in acellula domains (Ma hiesen
e al.2022). In pa ien s wi h ea ly FMTC, i is di icul o dis in-
guish i om he MEN2A synd ome. The main di e ence is he
ollow- up pe iod, in which subjec s wi h FMTC synd ome did
no de elop pheoch omocy oma o p ima y hype pa a hy oid-
ism (Wells e al.2015).
1.3.2 | Spo adic RET Poin Mu a ions
Soma ic RET poin mu a ions a e also ound in spo adic
MTCs, wi h M918T being he mos common pa hogenic a i-
an . Indels ha e been also desc ibed (Ciampi e al.2019; Elisei
e al.2022).
1.3.3 | RET Fusions
RET usions a e ela ed o DTCs and epo ed in 10%–20% o PTCs
(Fagin, K ishnamoo hy, and Landa2023; Cance Genome A las
FIGURE 1 | (A) RET pa hway. (B) The mos p e alen pa hogenic a ian o RET in MTCs, including V804, a esis ance amino acid change o
RET- selec i e inhibi o s. (C) The mos p e alen ea angemen s in FC- TC.
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4 o 11 Ame ican Jou nal o Medical Gene ics Pa C: Semina s in Medical Gene ics, 2025
Resea ch Ne wo k 2014). The mos p e alen ea angemen
occu ed in he RET in on 11. Coiled- coil domain- con aining
6 (CCDC6) RET (called RET–PTC1) and nuclea ecep o co-
ac i a o 4 (NCOA4) RET (known as RET–PTC3) a e he mos
equen RET usion pa ne s in PTCs. These al e a ions ha e
been p edominan ly epo ed in pedia ic (F anco e al.2022)
cases and adia ion- induced (Mo on e al. 2021) TC. Lymph
node and dis an me as ases we e mo e common in pa ien s wi h
RET- PTC3 (Peko a e al.2023).
Fusions a e mu ually exclusi e wi h each o he and wi h o he
se led pa hogenic a ian s in ollicula hy oid ca cinogene-
sis (e.g., RAS and BRAF). Younge age is a signi ican ac o in
he de elopmen o posi i e RET usions in PTCs. O he usions
epo ed in he li e a u e include KIF5B, PRKAR1A, KTN1, o
TRIM24 gene (Sal a o e, San o o, and Schlumbe ge 2021).
1.4 | RET Inhibi o s in TC
Ad ances in bioma ke de ec ion and genomic sequencing
ha e led o he de elopmen o no el a ge ed d ugs. MKi wi h
an an i- angiogenic p o ile signi ican ly imp o es p og ession-
ee su i al (PFS) in pa ien s. O e he yea s, hey ha e been
on he on line o ad anced DTC and MTC ea men (Gild
e al.2011). No able examples o DTC ea men in a adioiodine-
e ac o y se ing include so a enib (B ose e al.2014), len a inib
(Schlumbe ge e al.2015), and cabozan inib (B ose e al.2022),
all o which mainly a ge he VEGFR. All Phase 3 ials showed
an impac on PFS compa ed wi h placebo and signi ican o e all
esponse a es (ORRs).
MKi used in MTC se ings includes ande anib (Wells
e al. 2012) and cabozan inib (Elisei e al. 2013). Vande anib
is e ec i e agains pa hogenic a ian s in VEGFR2, RET, and
EGFR p o eins, whe eas cabozan inib ac s in he same manne
as VEGFR2, RET, and MET kinases. Clinical ials ha e shown
a ema kable enhancemen in PFS and ORR compa ed wi h pla-
cebo (Wells e al.2012; Elisei e al.2013).
Despi e he clinically meaning ul impac o hese d ugs, MKi
disad an ages include limi ed e icacy and high a es o ad-
e se e en s epo ed wi h implica ions o quali y o li e,
mainly as henia and hype ension (Liu e al. 2016; Høje
Wang e al.2023). MKi can inhibi RET pa hogenic a ian s,
bu only he M918T a nanomola concen a ion (Seoane and
Capde ila 2018). Fu he mo e, hese d ugs we e ine ec i e
agains he RET V804 ga ekeepe mu a ions (Ca lomagno and
San o o 2004; Nakaoku e al.2018; Dagogo- Jack e al.2018;
Wi h e al.2019).
Selec i e RET inhibi o s (RETi) ha e been used o ea RET-
mu an cance s. Selpe ca inib (LOXO- 292) is an ATP- compe i i e,
selec i e RET kinase inhibi o . I s an i umo ac i i y is s ong
in human cance cell lines and xenog a s (Subbiah, Velche i
e al. 2018). The clinical ial LIBRETTO 001 (NCT03157128)
demons a ed imp essi e esul s ac oss h ee coho s, includ-
ing p e iously ea ed and ea men - naï e pa ien s wi h RET
pa hogenic a ian s (subjec s wi h MTC), as well as RET usions
(pa ien s wi h PTCs); ORR and 1y- PFS we e 69%/82%, 73%/92%,
and 79%/64%, espec i ely (Wi h e al. 2020). In he Phase 3
LIBRETTO- 531 ial, selpe ca inib exhibi ed supe io e icacy
compa ed wi h MKi ( ande anib o cabozan inib) in ea men -
naï e MTC pa ien s, wi h 69 e sus 38% ORR and 86 e sus 65%
1y- PFS, espec i ely (Hadoux e al.2023).
P alse inib ( o me ly BLU- 667) is a highly selec i e small RETi. I
demons a ed imp essi e ou comes compa ed wi h MKi in in i o
and in i o models (Subbiah, Gaino e al.2018). The ARROW
(NCT03037385) Phase 1 ial explo ed i s e icacy in h ee di e -
en coho s. The p e ea ed RET mu an had an ORR o 60% and a
1y- PFS o 75%. In RET mu a ion- naï e pa ien s, ORR was 71% and
81%, espec i ely. RET usions esul ed in an ORR o 89% and PFS
o 81% (Subbiah, Hu e al.2021). These e icacy da a we e main-
ained o u he ial (Subbiah, Hu e al.2024).
The oxici y p o iles o bo h d ugs we e be e han hose o
MKi. LIBRETTO 531 epo ed a be e oxici y p o ile wi h
selpe ca inib han wi h he s anda d he apy. RETi may cause
noncon en ional ad e se e en s (such as chylous e usion and
gas oin es inal side e ec s du ing selpe ca inib ea men ) ha
a e no obse ed wi h MKi adminis a ion (Hadoux e al.2023).
Bo h RET- selec i e inhibi o s can a ge RET pa hogenic
a ian s, including he V804 ga ekeepe mu a ions ela ed o
esis ance o MKi. Howe e , new po en ial esis ance RET
pa hogenic a ian s ha e been desc ibed as esis ance (Elisei
e al.2013) mechanisms o RETi, such as 806 and 810 RET ami-
noacids (Subbiah, Shen e al.2021). New- gene a ion RETi a e
cu en ly unde de elopmen o Phase I ials.
In his e iew, we analyzed he mos common RET pa hogenic
a ian s in TC and hei po en ial implica ions o he e icacy
o RETi.
2 | Me hods
The pa hogenici y o RET a ian s was con as ed wi h he
li e a u e in he da abases OncoKB (Chak a a y e al. 2017;
Suehnholz e al. 2024), and COSMIC (Ta e e al. 2019;
COSMICn.d.).
The c i e ia o including clinical ials in he e iew we e RET-
selec i e inhibi o ials ha ecei ed FDA o EMA app o al
o clinical use in TC since 2020. These we e only he ials o
selpe ca inib and p alse inib. Clinical ials ha did no ob ain
app o al we e excluded.
Da a om he wa e all plo s o he igu es epo ed in ARROW
(Subbiah, Hu e al. 2024) (clinical ial o p alse inib) and
LIBRETTO (Wi h e al.2020) (clinical ial o selpe ca inib) we e
ex ac ed o s udy he maximum change in umo size. Th ee cu -
o s we e used: 30%, he a e es ablished by Response E alua ion
C i e ia in Solid Tumo s (RECIST) .1.1. p o ocol (Eisenhaue
e al.2009), 80%, and 100% (comple e esponse by RECIST .1.1).
RET pa hogenic a ian s we e independen ly s udied based on
his ological subg oups.
Va iables (pa hogenic a ian s, d ug adminis a ed, and he
achie emen o he di e en cu - o s) codi ied as quali a i e
ea u es we e analyzed using a wo- ailed Fishe 's exac es in
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5 o 11
IBM SPSS S a is ics 29.0.1.0. S a is ical signi icance was se
a p ≤ 0.05. A endency o co ela ion was assumed be ween p-
alues o 0.05 and 0.170. The p- alues be ween 0.170 and 0.250
we e ma ked in he ables as weak associa ion ends.
3 | RET Pa hogenic Va ian s in TC Published
Coho s
3.1 | He edi a y RET Poin Mu a ions
Cha ac e iza ion o la ge he edi a y MEN2 MTC coho s (Maciel
e al. 2019; Romei e al. 2010; Machens e al. 2013; Lebeaul
e al.2017) (Figu eS1) e ealed ha he mos p e alen pa ho-
genic a ian s in all s udies we e he ones ha imply a change in
he amino acid si e C634. Some di e ences ha e been epo ed
among di e en casuis ics and o igins. The second p e alen
pa hogenic a ian depends on he su ey was M918T o V804.
G533 amino acid had one o he highes p e alence a es in a
B azilian coho . Changes in he amino acid si e L790 we e mo e
equen in F ench and Ge man s udies han in V804. I alian
epo s ha e also shown di e ences wi h a high p e alence o
S891 amino acid changes.
3.2 | Spo adic RET Poin Mu a ions
Rega ding one o he la ges spo adic MTCs coho (Ciampi
e al. 2019), he esul s o 148 pa ien s showed ha he mos
p e alen poin mu a ion was M918T (40.5%). This pa hogenic
a ian coexis ed wi h o he s in six cases ( h ee wi h RET and
h ee wi h RAS a ian s). The second mos p e alen pa hogenic
a ian s we e he changes in he amino acid C643 (12.2%).
RET indels we e ound in 14 (9.5%) pa ien s. Few s udies ha e
in es iga ed RET indels. Elisei e al. epo ed ha hese pa ho-
genic a ian s a e ela ed o agg essi e beha io . The e icacy
o selpe ca inib was de ailed o wo pa ien s, who epo ed a
meaning ul umo esponse (Elisei e al.2022).
The pa hogenic a ian s speci ically s udied in LIBRETTO and
ARROW we e M918T and he changes in he amino acid si e
V804, espec i ely. Two o he a ian g oups we e analyzed:
hose ha a ec ed he cys eine- ich ex acellula domain (EC)
and o he ha we e no p e iously named.
3.3 | RET Fusions
Analyzing he cBiopo al .6.0.2 da abase, in which only
h ee s udies o FC- TC a e a ailable, 807 samples (500 PTCs
o TCGA, (Cance Genome A las Resea ch Ne wo k2014), 117
samples o he Landa e al.(2016) s udy one PDTCs and ATCs,
and 190 ATCs om he GATCI ini ia i e (Zeng e al.2024))
we e s udied, and 8% showed a RET pa hogenic a ian . O he
PTC coho (Cance Genome A las Resea ch Ne wo k2014),
7% showed pa hogenic a ian s, one case epo ed a poin
mu a ion V945M, 35 ha bo ed a s uc u al a ian , and wo
pa ien s also had a homozygous dele ion. The mos p e a-
len ea angemen was CCDC6- RET (17/35), ollowed by
he NCOA4- RET usion (5/35). No e ha bo h subjec s wi h
homozygous dele ions also ha bo ed an NCOA4- RET usion.
In he a icle by Landa e al.(2016), 4% (5/117) o he cases
showed RET ea angemen s. All he subjec s wi h al e ed
RET in his coho we e PDTCs. O he i e cases, h ee e-
po ed RET- PTC1 usion and he o he epo ed RET- PTC3
usion. None heless, ega ding he GATCI a icle (Zeng
e al.2024), 13% o he ATCs epo ed pa hogenic a ian s in
RET. Su p isingly, usion was no obse ed. Ten pa ien s had
ampli ica ions and 8 homozygous dele ions. Th ee pa ien s
ha bo ed RET pa hogenic a ian s in he ex acellula egion.
Based on his da a, he mos p e alen usions we e ep esen ed
in he ARROW analysis o p alse inib (Subbiah, Hu e al.2021,
2024) (CCDC6- RET and NCOA4- RET). O he usions we e
included in he same g oup o analyses. Despi e RET usions,
pa ien s we e also included in he clinical ial LIBRETTO,
and esponse a es we e epo ed o speci ic ea angemen s.
Ne e heless, o he s udies ha e demons a ed ha selpe ca i-
nib esponds signi ican ly o RET- usion- al e ed umo s (Dias-
San aga a e al.2020; D ilon e al.2023).
4 | Sensi i i y o Al e a ions o Selec i e RETi
Di e en RET pa hogenic a ian s ha e shown speci ic e icacy
ou comes o selec i e RETi in pa ien s wi h MTC and FC- TC.
The comple e da ase s o ORR and PFS o speci ic pa hogenic
a ian s ha e no been epo ed in published clinical ials. Bo h
s udies (LIBRETTO and ARROW) demons a ed di e ences
in ORR and PFS among he h ee g oups analyzed (Table2).
LIBRETTO esul s e ealed ha he highes ORR and 12- mon h
PFS among pa ien s wi h MTC we e ob ained in naï e cases,
which occu ed in ARROW.
Pa ien s wi h FC- TC exhibi ed he highes ORR in bo h he clin-
ical ials. Howe e , al hough mo e han hal o he pa ien s ob-
ain a 12- mon hs PFS wi h LIBRETTO and ARROW, he e was
a di e ence o 64% and 87%, espec i ely.
The maximum change in umo size in he LIBRETTO- 001
g oup o pa ien s wi h MTC is gi en in Table 3. Among he
ea ed cases, 71.4% (20/28) wi h he M918T pa hogenic a ian
achie ed 30% educ ion. A weak in e se endency was obse ed
o his associa ion (p = 0.160). I is wo h men ioning ha jus
i e pa ien s in his coho achie ed a o al esponse, and 80% o
hem (4/5) epo ed he M918T pa hogenic a ian .
Rega ding naï e pa ien s, he associa ion o M918T pa ien s
wi h 30% baseline showed a end (p = 0.159).
Among he EC- mu a ed cases, 67% showed a 30% esponse a e,
which esul ed in an in e se endency o associa ion (p = 0.094).
Only se en o he 79 naï e pa ien s showed a comple e e-
sponse. S ikingly, 71.4% (5/7) o he pa ien s exhibi ed he
M918T pa hogenic a ian . RET usion coho esul s we e no
epo ed conside ing he pe cen age o umo size educ ion in
LIBRETTO- 001.
Conside ing all MTC pa ien s desc ibed in LIBRETTO- 001
(n = 127), no endency o signi ican associa ion was obse ed
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6 o 11 Ame ican Jou nal o Medical Gene ics Pa C: Semina s in Medical Gene ics, 2025
(Table 3). 81% o M918T cases had a a e o a leas 30%.
In e es ingly, o he pa ien s who achie ed o al umo educ-
ion, 75% (9/12) we e M918T mu an cases. The e was no sig-
ni ican di e ence be ween naï e and MKi p e ea ed pa ien s
in selpe ca inib umo esponse, conside ing he change in
umo size.
The ARROW clinical ial was analyzed acco ding o he
size o umo educ ion using h ee p e iously desc ibed
baselines.
Table4A p esen s he esul s o he ARROW sepa a ed in o
naï e and ea ed pa ien s wi h MTC. No ably, all pa ien s
(4/4) who epo ed o al umo sh inkage exhibi ed he M918T
pa hogenic a ian . Th ee ARROW- ea ed pa ien s ha bo ed
he M918T a ian , coexis ing wi h he change in he amino
acid si e V804. These pa ien s we e iden i ied as M918T pa-
ien s in his s udy.
A coho o naï e pa ien s was e alua ed using he same c i e ia.
In pa icula , he only subjec ha eached a comple e educ ion
TABLE 3 | Associa ions be ween umo size educ ion and speci ic pa hogenic a ian s in LIBRETTO- 001 pa ien s ea ed wi h selpe ca inib.
No e: All pa ien s we e diagnosed wi h MTC (Medulla y hy oid cance ). Numbe s wi h * indica e in e se ela ionships.
Abb e ia ion: EC, ex acellula domain.
TABLE 2 | PFS (p og ession- ee su i al) and ORR (objec i e esponse a e) o ARROW and LIBRETTO.
LIBRETTO
00138
LIBRETTO
53139
ARROW
(2021)41
ARROW
(2024)42
RET mu an
ea ed
(MTC)
n=55
ORR=69%
PFS=82%
n=61
ORR=60%
PFS=82%
n=67
ORR=52%
PFS=74%
RET mu an
naï e
(MTC)
n=88
ORR=73%
PFS=92%
n=291
ORR=69%
PFS=86%
n=23
ORR=71%
PFS=81%
n=67
ORR=72%
PFS=85%
RET usions
(FC-TC)
n=19
ORR=79%
PFS=64%
n=11
ORR=89%
PFS=81%
n=25
ORR=84%
PFS=87%
No e: PFS was calcula ed as 12 mon hs' a e, % [95% CI].
Abb e ia ions: FC- TC, ollicula cell de i ed- hy oid cance ; MTC, medulla y hy oid cance .
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7 o 11
among he naï e mu an cases in ARROW ha bo ed an EC
pa hogenic a ian .
Mo eo e , only one pa ien ha bo ed he change in he amino
acid V804. An in e se endency o V804 and an associa ion o
achie ing a umo esponse o 30% we e obse ed (p = 0.164).
In he FC- TC coho , we ound di e ences in he a ailabili y o
RET usion in o ma ion be ween ARROW and LIBRETTO- 001.
Twen y- wo pa ien s wi h RET usions, p e iously ea ed wi h
sys ema ic he apies, we e s udied using ARROW (Table 4B).
Speci ic usions used we e CCDC6- RET and NCOA4- RET. The
emaining usions we e included in o he g oups. CCDC6- RET
cases had a 30% a e in 92.3% (12/13) o cases. A he second
baseline, his pe cen age was educed o 30.8% (4/13).
All pa ien s wi h NCOA4- RET achie ed 30% umo educ-
ion. Fo y pe cen o he subjec s achie ed 80%, and only one
achie ed a o al educ ion. No ably, only one RET usion gene
achie ed a 100% esponse. This ha bo ed an NCOA4- RET e-
a angemen (p = 0.227).
ARROW epo ed on 142 pa ien s o whom he umo esponse
a e was s udied. Howe e , due o he di e en his o ypes ana-
lyzed (MTCs and FC- TC) and hei dispa i ies in p ognosis, he e
could be a bias in analyzing he umo educ ion size oge he .
Taking all hese da a oge he , no associa ions o endencies we e
ound when RET- mu a ed pa ien s wi h ARROW we e analyzed
(MTC coho , Table4C). A weak end was obse ed be ween he
MKi- ea ed pa ien s and a be e esponse han ha o he naï e
pa ien s.
The p e alence o achie ing a 30% cu o o pa hogenic a ian s
was 79% (95/120). The numbe o pa ien s in he 80% g oup de-
c eased o 15 (13%). This educ ion was also epo ed in he usion
g oup, in which almos 96% (21/22) o pa ien s eached 30%.
Ne e heless, only 32% (7/22) achie ed 80% size educ ion, and
4.5% (1/22) achie ed a comple e esponse.
A o al o 269 pooled MTC pa ien s we e analyzed in bo h ials.
To elucida e he di e en al e a ions in esponse o d ugs, no
ends we e es ablished ega ding umo size educ ion in pa-
ien s wi h RET pa hogenic a ian s (n = 247). M918T mu a ed
pa ien s showed a weak end in he o al esponse (p = 0.201)
and we e he mos p e alen a ian in he achie emen o cu -
o s (80%, 12%, and 9%).
The changes in he amino acid si e V804 showed he lowes
p e alence among all baselines (69%, 0%, and 0%).
Rega ding all RET mu an pa ien s desc ibed in clinical ials,
80% achie ed a 30% umo size educ ion. Howe e , only 11%
achie ed an 80% esponse and 7% achie ed a comple e educ ion.
No signi ican di e ences we e obse ed in esponse e icacy
ega ding he use o p e ious MKi.
TABLE 4 | Associa ions be ween educ ion in umo size and speci ic pa hogenic a ian s in ARROW 2024 pa ien s ea ed wi h p alse inib.
No e: The numbe s wi h * indica e an in e se ela ionship. (A) Pa ien s wi h RET- poin mu a ions (MTC cases). (B) RET- usion pa ien s (FC- TC cases). (C) Naï e and
ea ed RET- mu a ed g oups joined (MTC cases).
Abb e ia ions: EC, ex acellula domain; MTC, medulla y hy oid cance .
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8 o 11 Ame ican Jou nal o Medical Gene ics Pa C: Semina s in Medical Gene ics, 2025
In o al, 77% o ea ed pa ien s and 82% o un ea ed pa-
ien s achie ed a 30% a e. This indica ed a weak end in pa-
ien s p e iously ea ed wi h MKi and an 80% esponse a e
(p = 0.217).
Compa ing selpe ca inib and p alse inib esponses in he 247
RET- mu a ed subjec s, no endencies a ose wi h he associa ion
o d ug usage and he educ ion o 30% and 80% in umo size.
None heless, he comple e esponse showed a endency owa d
he use o selpe ca inib (p = 0.132). LIBRETTO- 001 epo ed a
o al educ ion in 9.4% o he pa ien s, whe eas in ARROW o
4.2% (Table5).
5 | Discussion
ARROW and LIBRETTO ha e been he mos ele an clinical
ials o selec i e RETi, and bo h ha e ma ked signi ican mile-
s ones in TC ea men .
F om a genomic poin o iew, he ORR o LIBRETTO- 001 and
ARROW (2021 and 2024) we e highe in he RET usion g oup
(79% and 89%–84%, espec i ely) han in RET- mu a ed pa ien s.
These esul s a e no unp edic able, and se e al s udies ha e
demons a ed ha usions espond be e o d ugs han poin
mu a ions do (Nikanjam e al. 2020). In con as , among he
MTC cases, RET- mu a ed pa ien s p e iously ea ed wi h MKi
had he lowes ORR in bo h s udies.
In MTC pa ien s wi h LIBRETTO- 001, EC pa hogenic a ian s
wi hou MKi ea men had he lowes ORR (p = 0.094), closely
ollowed by V804. Simila esul s o V804 ha e been epo ed in
ARROW, whe e no pa ien exceeded he second cu - o . Ga ekeepe
mu a ions ha e been a ho opic in RET esea ch owing o MKi e-
sis ance (Subbiah, Velche i e al.2018). Be e esul s o V804 we e
obse ed in MKi- ea ed pa ien s in bo h ials.
The speci ic analysis in he clinical ials o he changes in he
amino acid si es Y806 and G810 would ha e been in e es ing o
shed ligh on RETi esis ance. Sol en on mu a ions in RET
a ise in a c i ical egion o he RET p o ein ha di ec ly in e ac s
wi h kinase inhibi o s, ypically p oximal o he ATP- binding si e.
These pa hogenic a ian s induce con o ma ional al e a ions in
he p o ein s uc u e, which dis up s he binding a ini y o inhibi-
o s, he eby con ibu ing o he apeu ic esis ance in RET- a ge ed
ea men s (Subbiah, Shen e al.2021; Subbiah, Gouda e al.2024).
Resea ch on o he pa hogenic a ian s, such as L730V/I, could be
o in e es o de e mine he accu acy o selpe ca inib ea men in
con as o p alse inib. Shen e al. demons a ed ha L730V/I RET
pa hogenic a ian s a e esis an o p alse inib, bu no o selpe ca-
inib. These poin mu a ions di e om he changes in he amino
acid si e G810 in he oo o he sol en on egion. Al hough p a-
lse inib did no inhibi he g ow h o xenog a umo s, selpe ca i-
nib inhibi ed hese umo s in an animal model (Shen e al.2021).
When bo h s udies we e analyzed ega ding he pa hogenic a i-
an ou comes o pa ien s wi h MTC (n = 247), M918T had he bes
umo educ ion a es, showing a weak end wi h a comple e e-
sponse (p = 0.201). P e ious s udies ha e epo ed ha he pa ho-
genic a ian M918T equi es he lowes hal maximal inhibi o y
concen a ion (IC50) o p alse inib (Luo e al.2021) and selpe ca i-
nib (Seoane and Capde ila2018) compa ed wi h o he pa hogenic
a ian s and RET wild- ype (WT). This esul also suppo s he
conclusion o ano he s udy, which demons a ed ha di e en
ea men s could be mo e e ec i e depending on he speci ic RET
TABLE 5 | Associa ions be ween educ ion in umo size and speci ic mu a ions in ARROW 2024 and LIBRETO- 001.
No e: Numbe s wi h * indica e in e se ela ionships.
Abb e ia ions: EC, ex acellula domain; RETi, RET inhibi o s.
15524876, 0, Downloaded om h ps://onlinelib a y.wiley.com/doi/10.1002/ajmg.c.32127 by Uni e sidad De Valladolid, Wiley Online Lib a y on [26/02/2025]. See he Te ms and Condi ions (h ps://onlinelib a y.wiley.com/ e ms-and-condi ions) on Wiley Online Lib a y o ules o use; OA a icles a e go e ned by he applicable C ea i e Commons License
9 o 11
pa hogenic a ian p esen in TC (Rod íguez- An ona e al.2013).
Pa ien s wi h changes in he amino acid C634 o RET had highe
exp ession o VEGFR3, PDGFRB, and KIT, and could bene i
om d ugs ha a ge hese molecules. Howe e , o M918T RET-
mu an cases, d ugs a ge ing RET (such as selpe ca inib o p al-
se inib), among o he s, will be mo e e ec i e (Rod íguez- An ona
e al.2013). Ou esul s demons a e ha he pa hogenic a ian s
ha bo ed in he umo we e no signi ican ly di e en in esponse
o selpe ca inib o p alse inib in pa ien s wi h MTC.
Conside ing he FC- TC pa ien da a in he ARROW, 95.5% o pa-
ien s achie ed a leas 30% umo educ ion. Ne e heless, only
one pa ien go a comple e esponse. Only 22 pa ien s wi h RET u-
sions we e included in he analysis. Analyses o la ge coho s ha
can e alua e he e icacy o di e en usions a e ecommended.
Conside ing he limi a ions o he p esen e iew, in o ma ion
ega ding RET pa hogenic a ian s has no been epo ed as
ge mline o soma ic. S ikingly, LIBRETTO did no show e-
sul s o size educ ion o he usions, and ARROW analyzed
DTCs and ATCs, he p ognoses o which also had a la ge dis-
pa i y. Howe e , di e en pa hogenic a ian s ha e been ana-
lyzed in ARROW and LIBRETTO (Wi h e al.2020; Subbiah,
Hu e al.2024), which ep esen he mos p e alen RET a ian s
in he li e a u e (Maciel e al.2019; Romei e al.2010; Machens
e al.2013; Lebeaul e al.2017).
Selpe ca inib and p alse inib did no show signi ican di e -
ences in umo size educ ion. Howe e , he e was a endency o
ob ain a comple e umo esponse wi h selpe ca inib compa ed
wi h ha wi h p alse inib.
Cu en ly, se e al RETi a e in he ea ly phases o clinical ials and
he p eclinical s ages. Zelen inib (Bos on Pha maceu icals2023)
(BOS172738, NCT03780517) has demons a ed s ong nano-
mola po ency agains WT RET and RET pa hogenic a ian s,
including ga ekeepe mu a ions. Phase I o he s udy was
comple ed and he ORR was 44% o MTC pa ien s (Scho ski
e al. 2021). Vepa esin inib (TAS0953/HM06) is ano he selec-
i e RETi unde going Phase I/II (Helsinn Heal hca e SA2023)
(NCT04683250) wi h p omising esul s because o i s ac i i y
agains no only he p e iously men ioned pa hogenic a ian s
bu also agains sol en - on mu a ions (Miyazaki e al.2023).
O he RETi a e now in he i s de elopmen s ages, such as
SY5007 (Shouyao Holdings [Beijing] Co. LTD2023) o APS03118
(Applied Pha maceu ical Science Inc2023), pa ing he way o
nex - gene a ion RETi. The e is an unme need o desc ibe he
mechanisms o esis ance o RETi o de elop new s a egies o
his popula ion o TC pa ien s.
6 | Conclusions
RETi selpe ca inib and p alse inib a e ac i e agains all RET
pa hogenic a ian s, wi h high e icacy in bo h usions and poin
mu a ions, esul ing in a clinical esponse in MTCs and FC-
TC umo s. Despi e some ends in ORR and umo educ ion
pe cen age, all pa ien s wi h RET pa hogenic a ian s showed
clinical bene i s. Cu en ly, speci ic RET poin mu a ions and
usions a e p edic i e bioma ke s o RETi he apy in TC bu do
no allow he es ablishmen o e ec i e subg oups. Indi iduals
exhibi ing RET pa hogenic a ian s should be adminis e ed a se-
lec i e RETi a any s age o he he apeu ic p o ocol. The e o e,
no el bioma ke s o he assessmen o sensi i i y and esis ance
equi e u he in es iga ion.
Au ho Con ibu ions
Sa a Gil- Be nabé: concep ualiza ion, me hodology, o mal analy-
sis, and w i ing – o iginal D a . Lucía Ga cía- DeLaFuen e: alida-
ion and isualiza ion. Alejand o Ga cía- Ál a ez: w i ing – e iew
and edi ing. Ginesa Ga cía- Ros án: w i ing – e iew and edi ing
and supe ision. Jaume Capde ila: w i ing – e iew and edi ing and
supe ision. Jo ge He nando: concep ualiza ion, alida ion, w i ing –
e iew and edi ing, and supe ision.
Acknowledgmen s
We wish o hank Iñigo Landa o c i ically e iewing his a icle.
Con lic s o In e es
Jaume Capde ila: Pe sonal con lic s o in e es —Scien i ic con-
sul ancy ole (speake and ad iso y oles) om No a is, P ize ,
Ipsen, Exelixis, Baye , Eisai, Ad anced Accele a o Applica ions,
Amgen, Sano i, Roche, Lilly, Huchmed, ITM, Me ck Se ono, Ad anz,
Es e e. Resea ch suppo —Resea ch g an s om No a is, P ize ,
As azeneca, Ad anced Accele a o Applica ions, Eisai, Amgen,
Baye , Gilead, Roche, Ipsen, ITM. Jo ge He nando: Speake s' bu eau
and expe opinion—Eisai, Ipsen, No a is, Baye , Lilly, Adacap,
Angelini, and Leo Pha ma. Alejand o Ga cía Ál a ez: Pe sonal con-
lic o in e es —ADACAP (No a is), Ad anz, EISAI, Ipsen. The
emaining au ho s decla e ha hey ha e no known compe ing inan-
cial in e es s o pe sonal ela ionships ha could in luence he wo k
epo ed in his s udy.
Da a A ailabili y S a emen
The au ho s con i m ha he da a suppo ing he indings o his s udy
a e a ailable wi hin he a icle.
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