T h e n e w e ng l a n d j o u r na l o f m e dic i n e
Original Article
DB-OTO Gene Therapy for Inherited Deafness
V. Valayannopoulos,1 M. Bance,2 D.S. Carvalho,3 J.H. Greinwald, Jr.,4 S.A. Harvey,5
A. Ishiyama,6 E.C. Landry,7 H. Löwenheim,8 L.R. Lustig,9 M. Manrique,10 R. Nash,11
R. Polo,12 C.V. Pritchett,13 J.T. Rubinstein,14 A.E. Shearer,15 I. del Castillo,16,17
J.J. Anderson,1 C.E. Corrales,1,18 T.M. Quigley,1 W.J. Riggs,1 P. Weber,1 G. Wilson,1
S.C. Irvin,1 H.E. Hassan,1 Y. Chen,1 R. Liu,1 M.C. Drummond,1 L.R. Sabin,1
B.J. Musser,1 G.D. Yancopoulos,1 C.A. Kyratsous,1 G.A. Herman,1 A. Baras,1
and J.P. Whitton,1 for the CHORD Study Group*​​
A BS T R AC T
BACKGROUND
Genetic deficiency of otoferlin, a protein critical to synaptic transmission by the sensory hair cells of the ear, causes congenital deafness. Medicines to treat the condition
are lacking; children typically receive cochlear implants. DB-OTO is a dual adenoassociated virus 1 gene therapy that delivers human OTOF complementary DNA
(encoding otoferlin) regulated by a hair cell–specific promoter.
METHODS
We conducted an open-label, single-group, first-in-human registrational study to
evaluate DB-OTO. Children with OTOF variants and profound deafness (defined by
an average audiometric threshold of >90 decibel hearing level [dB HL], indicating
an inability to hear a gas-powered lawn mower) received an intracochlear infusion
of DB-OTO (7.2×1012 vector genomes per ear) in one or both ears. The primary
efficacy end point was an average threshold on behavioral pure-tone audiometry
(PTA) at week 24 of 70 dB HL or less, a clinical standard that generally avoids
cochlear implantation and enables natural acoustic hearing. A key secondary end
point was the presence of an auditory brain-stem response to a click stimulus at a
threshold at or below 90 dB normalized hearing level (db nHL) at week 24. Safety
assessments included adverse events, laboratory results, and vestibular testing.
The authors’ full names, academic degrees, and affiliations are listed at the end
of the article. Jonathon P. Whitton and
Vassili Valayannopoulos can be contacted at ­jonathon​.­whitton@​­regeneron​.­com
and ­vassili​.­valayannopoulos@​­regeneron​
.­com, respectively, or at Regeneron Pharmaceuticals, 777 Old Saw Mill River Rd.,
Tarrytown, NY 10591.
*A complete list of investigators and
contributors to the CHORD trial is provided in the Supplementary Appendix,
available at NEJM.org.
Vassili Valayannopoulos and Manohar
Bance and Gary A. Herman, Aris Baras, and
Jonathon P. Whitton contributed equally to
this article.
This article was published on October 12,
2025, at NEJM.org.
DOI: 10.1056/NEJMoa2400521
Copyright © 2025 Massachusetts Medical Society.
RESULTS
A total of 12 children have been enrolled in the study. After a single infusion of
DB-OTO, a PTA average threshold of 70 dB HL or less at week 24 (primary end
point) and an auditory brain-stem response at or below 90 dB nHL (key secondary
end point) were found in 9 of the 12 participants (75%; 95% confidence interval,
43 to 95; P = 1.1×10−13 for both end points). Six participants could hear soft speech
without assistive devices, and 3 had average normal hearing sensitivity. A total of
67 adverse events occurred or worsened during or after treatment, none of which
led to discontinued participation in the study.
CONCLUSIONS
DB-OTO gene therapy improved hearing in patients with OTOF-related deafness,
enabling natural acoustic hearing and normalizing hearing sensitivity in 3 of 12
treated patients. (Funded by Regeneron Pharmaceuticals; ClinicalTrials.gov number,
NCT05788536.)
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1
T h e n e w e ng l a n d j o u r na l o f m e dic i n e
C
Videos showing
delivery of the
gene therapy
are available at
NEJM.org
ongenital deafness affects 1.7 per
1000 babies born in the United States1 and
is predominantly caused by genetic deficiencies.2-5 Biallelic pathogenic variants in OTOF,
the gene encoding otoferlin, account for 1 to 3%
of cases of congenital genetic deafness.4,6-9 Otoferlin functions as a calcium sensor expressed in
inner hair cells and regulates synaptic transmission between sensory inner hair cells and the
cochlear nerve (Fig. 1).10
Children with pathogenic variants in OTOF are
typically born with profound deafness (a term we
use with due respect to those in the deaf, Deaf,
and hard-of-hearing communities who may prefer other terms), and their hearing does not spontaneously improve.11 Medicines for the treatment
of OTOF-related deafness are lacking, and management involves lifelong use of cochlear implants.
Although such implants provide a benefit,12 they
limit speech understanding and music appreciation, and use of the device is difficult in certain
settings.13,14
Despite their profound deafness, young children with otoferlin deficiency have cellular structures of the inner ear that remain intact,15,16 which
suggests that introducing otoferlin protein with
adeno-associated virus (AAV)–based gene therapy
could restore natural hearing. We developed a dual
AAV1 vector using a hair cell–specific promoter
(Myo15) that delivers OTOF specifically to hair
cells, with the intention of enabling synaptic transmission between sensory inner hair cells and the
cochlear nerve (Fig. 1). The use of the dual AAV
system enables delivery of genomic payloads that
exceed the packaging capacity of a single AAV.
We used a well-established surgical approach for
local DB-OTO delivery (Fig. 1 and Video 1), based
on the common surgical method for cochlear
implants. After preclinical studies,17 we initiated
a study to evaluate DB-OTO administration in one
or both ears. After seeing early efficacy signals in
the first participant, we amended the study to
make it registrational, with prespecified formal
hypothesis testing.
Me thods
Participants
Participants were younger than 18 years of age
and had biallelic OTOF variants and profound deafness (defined by an average audiometric threshold of >90 decibel hearing level [dB HL]; additional
definitions are provided in Table S1), clinical markers of intact outer hair-cell function (distortionproduct otoacoustic emissions or cochlear microphonics in the treated ear or ears), and no
evidence of temperature-sensitive fluctuations in
hearing. Key exclusion criteria included previous
gene therapy or a cochlear implant in the ear
designated for DB-OTO. The full list of eligibility
criteria is provided in the protocol.
Surgical Delivery
Study Design and Oversight
CHORD is an ongoing, open-label, phase 1–2
study, enrolling up to 30 patients (Fig. S1 in the
Supplementary Appendix, available with the full
text of this article at NEJM.org). In part A, partici2
pants received DB-OTO in one ear; the contralateral ear could have a cochlear implant or remain untreated. In part B, participants received
DB-OTO in both ears during a single session.
Participants received DB-OTO at a dose of
7.2×1012 vector genomes in a volume of 240 μl per
dose in one ear or in each ear. Safety and efficacy
were to be assessed for 48 weeks after treatment
and then annually for 4 years. All details of the
study methods are provided in the Supplementary Appendix.
Authors who were employees of Regeneron
Pharmaceuticals (the study funder) designed the
study and analyzed the data, and the first and
last authors wrote the first draft of the manuscript. The authors, along with a medical writer
employed by Regeneron, contributed to the writing and review of the submitted manuscript. The
authors vouch for the accuracy and completeness
of the data and for the fidelity of the study to the
protocol (available at NEJM.org).
The study was conducted in accordance with
Good Clinical Practice guidelines and local regulations, with approval from an independent ethics
committee or institutional review board at each
site. Written informed consent was obtained from
parents or caregivers, and assent was obtained
from children who were 7 years of age or older.
An independent data and safety monitoring committee reviewed safety and efficacy data.
While the participant was under general anesthesia, DB-OTO was administered as a single intracochlear infusion through the round window
membrane with the use of the well-established
mastoidectomy and facial recess approach for
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DB-OTO Gene Ther apy for Inherited Deafness
cochlear implantation. The addition of a lateral
We established a statistical benchmark using
semicircular canal fenestration allowed egress of the natural history of OTOF-related deafness based
displaced perilymph to prevent pressure in the on an exhaustive literature review through 2024,
cochlea (Fig. 1 and Video 1).
including a published meta-analysis11 and a retrospective chart review in patients with biallelic
End Points
OTOF variants at Ramon y Cajal University HosThe primary efficacy end point was an average pital, Madrid. After this analysis involving more
threshold on behavioral pure-tone audiometry than 200 patients with no observed spontaneous
(PTA) at week 24 of 70 dB HL or less, a clinical hearing improvement (0%; Clopper–Pearson 95%
standard that generally avoids cochlear implan- confidence interval [CI], 0 to 1.8), a 2% null retation and enables natural acoustic hearing. PTA sponse was chosen as a conservative upper-limit
measures hearing sensitivity and assesses detec- benchmark to ensure a robust evaluation.
tion thresholds across sound frequencies (0.125
Assuming a 60% response rate, we calculated
to 8 kHz). The PTA average threshold was the that a sample of 8 or more participants would
average hearing sensitivity across the frequencies provide greater than 99% power to detect that
that are most important for speech perception the percentage of participants attaining a PTA
(0.5 to 4 kHz). Lower thresholds indicate better average threshold of 70 dB HL or less was greater
hearing sensitivity (25 dB HL indicates the abil- than the maximum plausible null percentage of
ity to detect a whisper), whereas higher thresh- 2%. Primary and secondary end points were tested
olds indicate inability to detect loud sounds (>90 at a one-sided alpha level of 0.025 with exact bidB HL indicates an inability to detect the sound nomial tests. A hierarchical testing strategy was
of a gas-powered lawn mower). A key secondary used to control the familywise type I error rate.
end point was the presence of an auditory brain- Other end points are summarized descriptively.
stem response at or below 90 dB normalized
hearing level (nHL) at week 24. In participants
R e sult s
who received DB-OTO in both ears, the betterperforming ear was used to assess whether the Participants
criteria for the primary efficacy end point and One participant was excluded because of an inthis key secondary end point had been met. Other ability to complete behavioral testing (Fig. S2).
key secondary end points were measured at Twelve participants between 10 months and 16
week 48 and are not reported here.
years of age who had OTOF variants and proSpeech perception, evaluated as part of sec- found deafness were included in the study and
ondary end points, was measured with the Early assessed after at least 24 weeks of follow-up. The
Speech Perception test18 and clinician and paren- representativeness of the participants is shown
tal Global Impression Scales19; results are report- in Table S2. Nine participants received DB-OTO
ed for participants who were followed up beyond in one ear and either a cochlear implant or no
week 48. Exploratory end points included audi- treatment in the contralateral ear; 3 participants
tory and language assessments (Auditory Skills received DB-OTO in both ears. At baseline, 10
Checklist20). Details of the assessments are pro- participants had serum anti-AAV1 neutralizing
vided in the Supplementary Appendix. Safety and antibodies (Table 1); the antibody titers substanside-effect assessments included evaluations of tially increased by 2 weeks after treatment in most
adverse events, laboratory testing, vital signs, of the participants (Table S3). Anti-otoferlin antiphysical examination, and vestibular testing.
bodies were detected in nearly 50% of the participants after treatment; responses were mostly
Statistical Analysis
low-titer and transient, and tests for antibodies
The efficacy of DB-OTO was tested against a natu- became negative by week 12 in most of the parral history benchmark. The first protocol did not ticipants (data not shown).
include formal hypothesis testing; after seeing
early efficacy in the first participant, we amended Primary and Key Secondary End Points
the protocol to include hypothesis-testing at later At week 24, a level of hearing that generally avoids
prespecified time points (see the Supplementary the need for cochlear implants (PTA average
Appendix).
threshold of ≤70 dB HL), the primary efficacy end
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T h e n e w e ng l a n d j o u r na l o f m e dic i n e
A Design of DB-OTO Vector Gene Therapy
Suspension
Dual hybrid system
AAV1
Hair cell–specific
promoter
AAV1
Transgene
Vector recombination,
transcription, and splicing
INNER
HAIR
CEL L
mRNA
Otoferlin
B Intracochlear Infusion of DB-OTO
SCALA VESTIBULI
(perilymph)
Vestibulocochlear
nerve
Lateral semicircular
canal fenestration
SCALA MEDIA
(endolymph)
Cochlear
afferent nerve
fibers
Inner hair cells
Outer hair cells
Catheter
Cochlea
Basilar
membrane
(Access through
mastoidectomy
and facial recess)
Perforation in
round window
Cross section
DB-OTO infusion
into perilymph
DB-OTO
infusion
SCALA TYMPANI
(perilymph)
C Deafness Caused by Otoferlin Deficiency and Goal of DB-OTO Treatment
Before DB-OTO Therapy
INNE R
H A IR
C EL L
After DB-OTO Therapy
No vesicle fusion
No neurotransmitter release
Vesicle fusion
Neurotransmitter release
Synaptic vesicles
Otoferlin
Synaptic
ribbon
Afferent
nerve fibers
4
No signal
propagation
2+
Ca
SYNAPTIC
CLEFT
Ca2+
Fusion
machinery
AMPARs
Signal
propagation
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DB-OTO Gene Ther apy for Inherited Deafness
Figure 1 (facing page). DB-OTO — Concept and
Treatment Delivery.
In persons in whom OTOF (the gene encoding otoferlin) is functional, inner hair cells within the cochlea express otoferlin, a protein that acts as a calcium sensor
for synaptic vesicles at ribbon synapses, controlling
the neurotransmitter release necessary for nerve signaling and acoustic hearing. In persons with pathogenic variants in OTOF, the cellular structure of inner
hair cells remains intact but defects in otoferlin function lead to congenital profound deafness in most
cases. Panel A shows the design of DB-OTO. A dual
adeno-associated virus 1 (AAV1) vector carrying the
human OTOF transgene was developed that contains
a Myo15 promoter to drive the specific expression of
otoferlin in the sensory inner hair cells of the cochlea.
Panel B shows the delivery of DB-OTO. DB-OTO is
administered into the cochlea as a single infusion in a
well-established surgical procedure similar to cochlear
implantation. A catheter is inserted through a small
opening created in the round window of the cochlea,
and the suspension is infused at a fixed rate with a
syringe pump. A fenestration is created in the lateral
semicircular canal that allows egress of displaced perilymph and pressure. After delivery, the catheter is removed, the round window membrane is repaired with
muscle or fascia, and the fenestration is repaired with
autologous grafts such as fascia, bone pate, muscle,
or a combination of these. Panel C shows the way in
which DB-OTO works to restore hearing in persons
with otoferlin deficiency, which disrupts the fusion
and replenishment of vesicles in inner hair cells, halting the transmission of signals from inner hair cells to
the cochlear nerve. The goal of DB-OTO treatment is
to enable the expression of functional otoferlin in the
inner hair cells to an extent that permits transmission
of signal to the cochlear nerve at normal hearing thresholds. AMPAR denotes α-amino-3-hydroxy-5-methyl-4isoxazolepropionic acid receptor, AP alkaline phosphatase recombinogenic region, mRNA messenger RNA,
SA splice acceptor site, and SD splice donor site.
point, was found in 9 of 12 participants (75%;
Clopper–Pearson 95% CI, 43 to 95; P = 1.1×10−13),
in six of nine treated ears as compared with zero
of nine untreated ears among the participants
who received treatment in one ear, as well as in
the 3 participants who received treatment in
both ears (Fig. 2). Across cohorts, 6 participants
attained soft-speech sensitivity (≤45 dB HL) and
3 normal hearing sensitivity (≤25 dB HL) by
week 24 (Fig. 2A and Table S1). Of the 3 participants who did not meet the criterion for the primary efficacy end point, 1 (Participant 3) showed
no improvement. The other 2 participants (Participants 2 and 7) had positive changes with respect to baseline.
At baseline, neural responses at a threshold
above 90 dB nHL were absent in all participants
(Fig. 3). At week 24, an auditory brain-stem
response at or below 90 dB nHL, a key secondary end point, was found in 9 of the 12 participants (75%; Clopper–Pearson 95% CI, 43 to 95;
P = 1.1×10−13). Among the participants who received
treatment in one ear, we detected an auditory
brain-stem response in seven of nine treated ears,
as compared with zero of nine untreated ears
(Fig. 3). Two of the 3 participants who received
treatment in both ears had an auditory brain-stem
response detected.
Two participants were 16 years old at the time
of treatment. Both had improvements in hearing
in the DB-OTO–treated ear (Figs. 2B and 3). Eight
participants were followed up for more than 24
weeks (up to 72 weeks); the hearing in all 8 remained stable or continued to improve during this
interval (Fig. 2E).
Outcomes in Individual Participants
The criterion for the primary efficacy end point
was not met in Participant 2, although his hearing showed improvement after week 24. He attained a PTA average threshold of 33.75 dB HL
by week 48, corresponding to a hearing sensitivity that enables detection of soft sounds. Figure S3
shows individual audiograms obtained for each
patient at different times during follow-up. Participants 1 and 6 had focal reductions in hearing
sensitivity limited to the highest frequencies
(≥4.0 kHz). This frequency range corresponds to
the cochlear region closest to the round window
membrane (the infusion site). In Participant 1,
this reduction in hearing sensitivity at high frequencies was associated with persistent otitis
media and stabilized after resolution of the infection by week 48. In Participant 6, a transient
reversal in this sensitivity reduction occurred when
systemic glucocorticoid treatment was administered.
Secondary and Exploratory Outcomes
Speech Perception and Development
Speech development was assessed at 48 weeks on
the basis of parental and clinician reports, with
formal testing performed when developmentally
appropriate. Four participants reached the 48-week
time point or beyond. Participant 3 showed no
response (Fig. 2B) and subsequently received a
cochlear implant in the ear that had been treated
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T h e n e w e ng l a n d j o u r na l o f m e dic i n e
Table 1. Characteristics of the Participants at Baseline.*
Participant
No.
Sex
Age in
Years at
Infusion
OTOF Genotype†
Treatment
Right Ear
Anti-AAV1
Neutralizing
Antibody Titer
Left Ear
1
F
0.9
c.2676+1G→T/c.2887C→T (p.Arg963*)
DB-OTO
CI (concomitant)
1:5
2
M
4.0
c.4819C→T (p.Arg1607Trp) homozygous
DB-OTO
CI (concomitant)
1:5
1:10
3
F
1.3
c.2485C→T (p.Gln829*) homozygous
DB-OTO
No treatment
4
F
2.3
c.2485C→T (p.Gln829*) homozygous
No treatment
DB-OTO
1:5
5
M
4.1
c.762C→G (p.Tyr254)/c.1469C→G (p.Pro490Arg)
CI (previous)
DB-OTO
1:5
6
F
16.3
c.2485C→T (p.Gln829*) homozygous
CI (previous)
DB-OTO
1:5
7
F
16.4
c.5714G→A (p.Gly1905Asp) homozygous
CI (previous)
DB-OTO
Negative
8
F
1.9
c.2485C→T (p.Gln829*)/c.5566C→T (p.Arg1856Trp)
DB-OTO
No treatment
Negative
9
F
1.0
c.2239G→T (p.Glu747*) homozygous
DB-OTO
DB-OTO
1:5
10
F
2.8
c.1621G→A (p.Gly541Ser)/c.1961_1964dup
(p.Arg656Alafs*8)
CI (previous)
DB-OTO
1:320
11
M
1.3
c.2485C→T (p.Gln829*) homozygous
DB-OTO
DB-OTO
1:5
12
F
1.2
c.2485C→T (p.Gln829*)/c.5103+2T→A
DB-OTO
DB-OTO
1:10
*AAV1 denotes adeno-associated virus 1, and CI cochlear implant.
†Genotypes are based on the OTOF complementary DNA reference sequence NM_001287489.1.
Videos showing
hearing
improvements
in Participant 1
are available at
NEJM.org
6
with DB-OTO, 36 weeks after treatment; this par- speech perception. By week 72, with the cochlear
ticipant was therefore not subsequently assessed implant deactivated, he achieved 100% accuracy
for discerning syllable patterns and 50% accuracy
for efficacy.
for two-syllable word discrimination with no
visual cues on the Early Speech Perception Test.
Participants with Gene Therapy
An excerpt from the exit interview for this parand a Contralateral Cochlear Implant
Participant 1 was 10 months of age when she ticipant is provided in the Supplementary Apreceived DB-OTO in one ear and a cochlear im- pendix.
plant in the contralateral ear. By week 24, her hearing had improved to normal levels (18.75 dB HL) Participant with Gene Therapy Only
(Fig. 2A and Video 2B). At week 72, when she Participant 4 received DB-OTO in one ear, at 28
was 27 months of age, her parents and clinicians months of age, without treatment in the contrareported “much improvement” on the Global Im- lateral ear. By week 48, her parents reported “very
pression Scale of speech perception. She had 100% much improvement” and her clinicians “much
accuracy for two-syllable words and 50% accu- improvement” on the Global Impression Scale of
racy for single-syllable words without visual cues speech perception. Behavioral testing could not
(with her cochlear implant deactivated) on the be completed at that time. Her parents completed
Early Speech Perception test (Video 2D). Six months the Auditory Skills Checklist to assess auditory
later (at week 96), she achieved 100% accuracy development; the child’s score was 8% at basefor two-syllable words and 70% accuracy for sin- line and 60% at week 48. Excerpts from the exit
gle syllables.
interview for this participant are provided in the
Participant 2 was 4 years old when he re- Supplementary Appendix.
ceived treatment with DB-OTO in one ear and a
cochlear implant in the contralateral ear. He had Safety
no spoken or sign-language ability. At week 48, Many of the adverse events were temporally asparents and clinicians reported “minimal im- sociated with and reported by investigators to
provement” on the Global Impression Scale of be related to the surgical approach (Fig. 1 and
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DB-OTO Gene Ther apy for Inherited Deafness
Average Threshold (dB HL)
A PTA Average Threshold in Treated Participants (N=12)
0
80
1 12L
5
412R
11L
11R10
6 9L
89R
7
2
100
3
20
40
60
120
0
4
8
12
16
20
Hearing Ability
Normal
Hearing
Can hear whispers (25 dB HL)
Can hear soft speech (45 dB HL)
Can hear conversational speech (60 dB HL)
Can hear loud speech (80 dB HL)
Cannot hear gas-powered lawn mower (>90 dB HL)
Profound
Deafness
24
Week of Visit
C PTA Average Threshold in Untreated Ear in Participants in Part A
(N=9)
0
1
5
4
10
6
8
7
2
20
40
60
80
100
120
Average Threshold (dB HL)
Average Threshold (dB HL)
B PTA Average Threshold in Treated Ear in Participants in Part A (N=9)
3
0
4
8
12
16
20
24
0
20
40
60
80
100
120
4
0
4
8
Week of Visit
40
60
80
100
8
12
16
20
24
Week of Visit
Average Threshold (dB HL)
Average Threshold (dB HL)
12L
12R
11L
11R
9L
9R
20
4
20
E Durability of Response in Participants with Follow-up after Week 24 (N=8)
0
0
16
Week of Visit
D PTA Average Threshold in Each Ear in Participants in Part B (N=3)
120
12
10
5
8
7 321
6
24
0
20
4
5
9L
8
6
9R
7
40
60
80
1
2
100
120
0
8
16
24
32
40
48
72
Week of Visit
Figure 2. Changes in Pure-Tone Audiometry at Week 24.
Panel A shows changes in average threshold on behavioral pure-tone audiometry (PTA) from baseline to week 24 in 12 participants.
Each line represents a treated ear, and each point corresponds to the average threshold (measured in decibel hearing level [dB HL]) for
which a response was detected at each visit. In instances in which no response was detected for a given frequency, the maximum level
assessed was used for computing the average. The dashed line represents the threshold sensitivity corresponding to the primary efficacy end point (PTA average threshold of ≤70 dB HL). Line numbers indicate the order of treatment in the study. For patients who received
treatment in both ears, the left and right ear are indicated by L and R. Eleven of 12 participants had notable changes from baseline; the
criterion for the primary efficacy end point was met in 9 of 12 participants (75%; Clopper–Pearson 95% CI, 43 to 95; P = 1.1×10 −13), and 3
of 12 participants reached average normal hearing sensitivity levels (≤25 dB HL). Panel B shows the changes in the PTA average threshold from baseline to week 24 in 9 participants in part A of the study, who received DB-OTO in one ear; Panel C shows the outcomes in
the contralateral ear (untreated ear) in part A participants. Eight of the 9 participants in part A had notable changes from baseline and in
the treated ear as compared with the untreated ear. The criterion for the primary efficacy end point was met in 6 of the 9 participants.
Panel D shows the changes in the PTA average threshold from baseline to week 24 in the 3 participants in part B, who received DB-OTO
in both ears; the criterion for the primary efficacy end point was met in all 3. Panel E shows changes in average threshold on PTA in 8
participants who completed post–week 24 visits. Three participants completed the 48-week assessments, 1 participant completed an
unscheduled 67-week assessment (shown at week 72 in the graph), and 1 completed a 72-week assessment. In general, participants
showed sustained or improved hearing sensitivity relative to week 24. Participant 1 had a focal loss of hearing at the highest frequencies, which may have been related to chronic ear infection.
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T h e n e w e ng l a n d j o u r na l o f m e dic i n e
Video 1). Of the 67 adverse events that were reported as starting or worsening during or after
treatment (Table 2), 17 were considered to be
related to the surgical delivery of DB-OTO (Tables S4 and S5). Two serious adverse events occurred. One participant had grade 3 mastoiditis
associated with the cochlear implant in the ear
that had not been treated with DB-OTO, and
grade 3 walking instability developed in another
participant; the latter participant had recently
received a varicella vaccination. Both events resolved without sequelae. All remaining adverse
events during or after treatment were transient.
No persistent adverse vestibular findings were
identified (Table S5).
Table 2. Adverse Events.*
Part A
(Treatment in
One Ear)
(N = 9)
Event
Part B
(Treatment in
Both Ears)
(N = 3)
Overall
(N = 12)
no. of events
Adverse events
57
10
67
Adverse events leading to
study discontinuation
0
0
0
Adverse events leading to
dose interruption
0
0
0
*Adverse events shown in the table are those that began or worsened in severity on or after the date of administration.
Part A, treated
Percentage of Participants
Part A, untreated
100
90
80
70
60
50
40
30
20
10
0
Baseline
4
Part B, treated
6
12
All treated
24
Week
Figure 3. Auditory Brain-Stem Response at Week 24.
The percentage of participants with an auditory brain-stem response to a
click stimulus (a brief broadband sound that activates a wide range of frequencies in the cochlea) at a threshold at or below 90 dB normalized hearing level is shown. One participant who received treatment in both ears
(Part B) had a response to a click in one ear at week 12 but not at week 24.
None of the participants with an untreated ear showed improvement from
baseline in that ear.
8
Discussion
OTOF-related deafness results from genetic deficiency of a single protein, causing lifelong synaptic dysfunction and deafness.6,10 In this study,
DB-OTO gene therapy enabled children with congenital deafness to hear for the first time.
Most participants had dramatic improvements
that ended the need for cochlear implants and
enabled natural acoustic hearing. None of the untreated ears showed spontaneous improvement,
a finding consistent with those from our natural
history benchmark analysis. By 24 weeks after
treatment, several participants had had progression from an inability to hear a gas-powered lawn
mower to the ability to detect whispers, which
highlights intact inner ear structures that were
amenable to gene therapy. Contrary to prevailing
views that the efficacy of OTOF gene therapy
might be limited to participants who receive it
early in life, we observed benefits when DB-OTO
was given to participants as old as 16 years of age.
By intervening early, we expected DB-OTO to
promote speech and language development. Of
the four children followed for at least 48 weeks,
one showed no response and was not assessed
for efficacy outcomes after 36 weeks; the other
three were tested for speech perception, and the
resulting data provide supporting evidence that
they have been learning to recognize and produce
words and sounds in their native languages. One
participant also showed distant sound detection;
an inability to detect such sounds is a limitation
of cochlear implants.21
The inner ear encodes frequencies across its
length, with the middle region tuned for human
speech (0.5 to 4 kHz) and music appreciation requiring an even broader range. Hearing improvements generally occurred across all clinically assessed frequencies (0.125 to 8 kHz) after DB-OTO
treatment.
We initially treated one ear with DB-OTO,
then transitioned to simultaneous treatment of
both ears. No safety differences were observed,
and responses in each ear were similar in the first
three participants who received treatment in both
ears. We view bilateral treatment as key to maximizing the ability to localize sounds and understand speech in conditions characterized by ambient noise.
Because the targeted inner hair cells are terminally differentiated, we anticipate durable clin-
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DB-OTO Gene Ther apy for Inherited Deafness
ical benefit after a single infusion, since the introduced gene therapy should not be diluted through
cell replication. Data to date in the eight participants followed for more than 24 weeks support
a durable effect, although a decline in hearing
sensitivity at high frequencies was seen in two
participants, without a clinically significant effect on speech perception. Longer-term monitoring remains necessary. The reason for the normalization of hearing sensitivity in some patients
and not in others remains unclear, although this
phenomenon has also been observed in other
gene-therapy studies22-25 and in our preclinical
studies in the OtofQ828X/Q828X mouse model.17
The lack of a response in Participant 3 remains
unexplained. Other participants with similar
baseline characteristics and identical OTOF genotypes had hearing improvement. The surgical
delivery was uneventful, but this participant had
a relatively modest immune response to AAV1,
as indicated by the systemic neutralizing antibody titer, which may have indicated insufficient
delivery. The patient subsequently received a cochlear implant in the treated ear and had progression in hearing improvement, which supports the idea that DB-OTO treatment does not
preclude later implantation.
Because preclinical data had indicated that antibodies would not affect the efficacy of DB-OTO,
persons with high preexisting serum anti-AAV1
antibody titers were not excluded from the study.17
Most participants had low titers of anti-AAV1
antibodies at baseline; the highest titer at baseline was in a participant who had robust hearing
improvement after treatment. This finding suggests that, as with ocular applications,26-31 preexisting antibodies may not interfere with inner ear
AAV transduction efficiency and that repeat treatment could be considered for persons with insufficient responses to the first dose.24
Sensory restoration with gene therapy has been
challenging. For example, gene therapy has improved sensory function in vision loss,26-30 although assistive devices remain necessary because of limited normalization of visual acuity.
These limitations may, in part, be driven by cellular degeneration that is associated with these
conditions. Here we report normal hearing sensitivity by 6 months after treatment (with no device correction) in 3 of 12 participants, as well as
improvements in speech perception at 1 year in
all 3 of the participants who both met the crite-
rion for the primary efficacy end point and underwent such testing. Although the sample size
is small, these findings suggest that normalization of sensory function is possible with geneaddition therapy in cases in which the cellular
substrate is intact.
Limitations of the study include its small size
and its limited duration. In addition, it was converted to a registrational study, and therefore
some end points were not prespecified initially.
However, the decision to amend the study and
propose formal testing was made after only partial data in the first participant had been obtained and before this participant had met the
criterion for the proposed end point. Moreover,
a sensitivity analysis excluding this first participant produced consistent and significant results
(see the Supplementary Appendix).
Our results support further clinical investigation of the potential of DB-OTO to treat congenital deafness caused by pathogenic variants
in OTOF. In our ongoing study, we plan to assess
outcomes for 5 years after DB-OTO treatment.
Whether other forms of deafness will benefit
from similar strategies remains to be determined.32
Supported by Regeneron Pharmaceuticals.
Disclosure forms provided by the authors are available with
the full text of this article at NEJM.org.
A data sharing statement provided by the authors is available
with the full text of this article at NEJM.org.
We thank the study participants, their families, the investigational site members involved in the study, former employees of
Decibel Therapeutics who have worked on the auditory sciences
program, the members of the data and safety monitoring board
(Nicola Longo, M.D, Ph.D., Anthony A. Mikulec, M.D., and Ian
M. Windmill, Ph.D), the members of the Patient Advocacy Group
Council and Patient/Parent/Caregiver Advisory Board, and Hannah H. Chang, Ph.D., of Regeneron Pharmaceuticals for providing writing support and developing the submitted manuscript
according to the Good Publication Practice guidelines. Development and support for earlier versions of the figures were provided by Prime Global (Knutsford, United Kingdom) and funded
by Regeneron Pharmaceuticals.
Author Information
Vassili Valayannopoulos, M.D., Ph.D.,1 Manohar Bance, M.B.,
Ch.B.,2 Daniela S. Carvalho, M.D.,3 John H. Greinwald, Jr.,
M.D.,4 Steven A. Harvey, M.D.,5 Akira Ishiyama, M.D.,6 Evie C.
Landry, M.D.,7 Hubert Löwenheim, M.D.,8 Lawrence R. Lustig,
M.D.,9 Manuel Manrique, M.D., Ph.D.,10 Robert Nash, M.B.,
Ch.B.,11 Rubén Polo, M.D., Ph.D.,12 Cedric V. Pritchett, M.D.,
M.P.H.,13 Jay T. Rubinstein, M.D., Ph.D.,14 A. Eliot Shearer, M.D.,
Ph.D.,15 Ignacio del Castillo, Ph.D.,16,17 Jeffery J. Anderson,
Ph.D.,1 C. Eduardo Corrales, M.D.,1,18 Tera M. Quigley, Au.D.,1
William J. Riggs, Ph.D., Au.D.,1 Peter Weber, M.D.,1 Gary Wilson, Ph.D.,1 Susan C. Irvin, Ph.D.,1 Hazem E. Hassan, Ph.D.,
R.Ph.,1 Yanping Chen, Ph.D.,1 Rong Liu, M.D., Ph.D.,1 Meghan C.
Drummond, Ph.D.,1 Leah R. Sabin, Ph.D.,1 Bret J. Musser,
Ph.D.,1 George D. Yancopoulos, M.D., Ph.D.,1 Christos A. Kyrat-
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9
T h e n e w e ng l a n d j o u r na l o f m e dic i n e
sous, Ph.D.,1 Gary A. Herman, M.D.,1 Aris Baras, M.D.,1 and
Jonathon P. Whitton, Au.D., Ph.D.1
1
Regeneron Pharmaceuticals, Tarrytown, NY; 2 University of Cambridge, Cambridge, United Kingdom; 3 Department of Otolaryngology Head and Neck Surgery, University of California, San Diego, La Jolla; 4 Cincinnati Children’s Hospital, University of
Cincinnati, Cincinnati; 5 Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, Wauwatosa;
6
UCLA School of Medicine, Los Angeles; 7 Nemours Children’s
Health, Jacksonville, FL; 8 Department of Otolaryngology–Head
and Neck Surgery and Hearing Research Center, University of
Tübingen Medical Center, Tübingen, Germany; 9 Department of
Otolaryngology–Head and Neck Surgery, Columbia University
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