Inclusion criteria
1. Must have given written informed consent before any study-related activities are carried out and must be
able to understand the full nature and purpose of the study, including possible risks and adverse effects.
2. Adult males and females ≥ 18-75 years of age (inclusive) at Screening.
3. Weight range between 40 kg and 120 kg at Screening.
4. A diagnosis of CIDP or possible CIDP per the 2021 European Academy of Neurology (EAN)/Peripheral
Nerve Society (PNS) guidelines. Participants must have either typical CIDP or one of the following
variants: motor or multifocal CIDP. Diagnosis must be confirmed by the ICRP.
5. CIDP Disease Activity Status (CDAS) score ≥ 3 at Screening.
6. Must be neurologically stable (ie, no relapses or other neurological events that could affect
examinations) at Screening and confirmed prior to Day 1 of Part A.
However, if a participant experiences clinically meaningful deterioration during tapering of oral
corticosteroids, the Investigator may request up to an additional 3 weeks of Screening to allow the
participant to stabilize prior to Day 1 of Part A. Clinically meaningful deterioration during corticosteroid
tapering is defined as at least one of the following:
a. ≥ 1-point increase in adjusted INCAT score
b. ≥ 4 points decrease in I-RODS total score
c. ≥ 3 points decrease in MRC-SS
d. ≥ 8 kilopascal worsening in mean grip strength (one hand) or
e. a significant deterioration in the participant's health per the Investigator's judgment
7. Must have an adjusted INCAT score between 2 and 9 inclusive at Screening and confirmed on Day 1 of
Part A prior to dosing. Participants with an adjusted INCAT score of 2 at study entry must have this
score exclusively from the leg disability subscore.
Protocol Version 1.1 DNTH103-CIDP-301
Confidential 20
8. Must fulfill one of the following treatment conditions for CIDP:
a. Currently treated with and responded to Ig (IVIg or SCIg) alone or Ig (IVIg or SCIg) plus oral
corticosteroids, or previously treated with and responded to, but no longer have access to, Ig (IVIg
or SCIg) alone or Ig (IVIg or SCIg) plus oral corticosteroids.
b. Currently treated with and responded to only oral corticosteroids, or previously treated with and
responded to, but no longer have access to, oral corticosteroids.
c. Refractory participants who have had failure (worsened) or an inadequate response (defined as no
clinically meaningful improvement after treatment for a minimum of 12 weeks on Ig and/or oral
corticosteroids) or are unable to tolerate these treatments due to side effects. Clinically meaningful
improvement is defined as one of the following:
• ≥ 1-point decrease in adjusted INCAT score,
• ≥ 4 points increase in I-RODS total score,
• ≥ 3 points increase in MRC-SS,
• ≥ 8 kilopascal improvement in mean grip strength (one hand), or
• an equivalent improvement based on information documented in medical records and per
the Investigator's judgment.
d. Treatment naïve with no history of prior treatment for CIDP
9. Participants on Ig, corticosteroids, or immunosuppressant drugs must adhere to the following stability
requirements:
a. If currently treated with Ig, must have received a stable maintenance dose for at least 3 cycles or
6 weeks, whichever is longer, prior to Screening and then remain on the same stable maintenance
dose until enrollment on Day 1 of Part A with the typical IV maintenance dosing of 0.4-1.0 g/kg
every 2-6 weeks (or 0.1-1.0 g/kg for SCIg every 1-4 weeks). For IVIg, higher maintenance doses
than 1 g/kg every 2-6 weeks, or regimens further apart than 6 weeks between doses will not be
allowed. For SCIg, higher maintenance doses than 0.1-1.0 g/kg every 1-4 weeks or regimens further
apart than 4 weeks between doses will not be allowed. Participants who are on Ig must be willing to
stop Ig 1 week prior to Part A Day 1.
b. If currently treated with oral corticosteroids, must have been taking oral corticosteroids for at least
4 weeks (28 days) prior to entering Screening, with doses not exceeding 40 mg/day of prednisone or
its equivalent at Screening. Participants must be willing to taper corticosteroid use as specified
below:
• Participants on oral corticosteroids alone must be willing to taper their corticosteroids to
50% of their starting dose by Day 1 of Part A and to remain on that dose throughout Part A
and Part B.
• Participants who are on Ig and oral corticosteroids must be willing to taper the dose of
corticosteroids to be equivalent to no more than an oral prednisone dose ≤ 10 mg/day by
Day 1 of Part A and to remain on that dose throughout Part A and Part B.
• Tapering of corticosteroids should begin as soon as possible after entering Screening
(within the first week) and the Investigator should complete the taper 1 week prior to
enrollment into Part A.
c. If refractory to Ig and/or oral corticosteroids as defined in Inclusion Criterion 8c, no treatment with
Ig, cyclosporine, or cyclophosphamide within 8 weeks prior to Screening will be allowed. Certain
immunosuppressant drugs (azathioprine or mycophenolate mofetil) are allowed at Screening if taken
at a stable dose for ≥ 3 months prior to Screening. Oral corticosteroids are allowed if participant is
on a stable dose of < 20 mg/day of prednisone (or equivalent dose for other oral corticosteroids) for
≥ 3 months prior to Screening.
Note: For participants on oral corticosteroids who have neurologic worsening during tapering, see
Inclusion criterion 6.
10. Participants must have documented vaccinations against N. meningitidis, including serogroup B
meningococcus, where available, within 3 years of enrollment or be vaccinated at least 2 weeks
Protocol Version 1.1 DNTH103-CIDP-301
Confidential 21
(14 days) prior to Part A Day 1. They should also have documented vaccinations against S. pneumoniae
and/or H. influenzae within 3 years prior to enrollment or be vaccinated at least 2 weeks (14 days) prior
to Part A Day 1 in accordance with local requirements and based on vaccine availability.
11. Female participants must:
a. Be of nonchildbearing potential, ie, surgically sterilized via laparoscopic methods at least 6 weeks
before Screening, if surgically sterilized via open abdominal surgery, at least 12 weeks before
Screening or postmenopausal (where postmenopausal is defined as no menses for 12 months without
an alternative medical cause and a follicle-stimulating hormone (FSH) level ≥ 40 IU/L at Screening),
or
b. If of childbearing potential, must agree not to donate ova, not to attempt to become pregnant and, if
engaging in sexual intercourse with a male partner, must agree to use a highly effective method of
contraception from signing the ICF throughout the study until the end of the Safety Follow-up
period, or longer if required in accordance with local requirements. Acceptable methods of
contraception are outlined in Section 13.1 of the protocol.
12. Male participants must be surgically sterile for at least 90 days prior to Screening or agree not to donate
sperm and, if engaging in sexual intercourse with a female partner who could become pregnant, must
agree to use an acceptable method of contraception from signing the ICF throughout the study until the
end of the Safety Follow-up period, or longer if required in accordance with local requirements.
Acceptable methods of contraception are outlined in Section 13.1 of the protocol.
13. No clinically significant abnormalities (in the opinion of the Investigator) at the Screening visit,
including:
a. No clinically significant findings in serum chemistry, hematology, coagulation, and urinalysis tests.
b. Triplicate 12-lead electrocardiogram (ECG) (taken after the participant has been supine for at least
5 minutes) with a mean QT interval corrected using the Fridericia method (QTcF) ≤ 450 msec for
males and ≤ 460 msec for females and no clinically significant abnormalities.
Note: Triplicate ECG assessments may be repeated once if abnormal values were recorded in the
first set of ECGs, at the discretion of the Investigator. ECG findings outside of normal ranges may be
considered acceptable if determined by the Investigator to be not clinically significant.
14. Be willing and able to comply with all study assessments and adhere to the protocol schedule and
restrictions.
Exclusion Criteria
Participants are excluded from the study if any of the following criteria apply:
Neurologic
1. Clinical signs or symptoms suggestive of polyneuropathy of other causes, such as inflammatory
neuropathies.
2. Any other neurologic or other disease that could better explain the participant's signs and symptoms or
that could cause signs/symptoms that could interfere with treatment or outcome assessments.
3. Diagnosis with CIDP variants not specified above per the 2021 EAN/PNS guidelines.
4. Known evidence of central demyelination or known history of myelopathy
General/Medical History
5. History or presence of significant medical/surgical condition including any acute illness or major
surgery considered to be clinically significant or that could have a potential impact on safety/efficacy or
study procedures in the opinion of the Investigator. A planned surgery during the treatment period may
be allowed in consultation with the Medical Monitor.
6. Any other condition, including mental illness or prior therapy that in the opinion of the Investigator
would make the participant unsuitable for this study, including inability to cooperate fully with the
requirements of the study protocol or likelihood of noncompliance with any study requirements.
7. Known complement deficiency or history of positive titer for anti-C1 antibodies.
Protocol Version 1.1 DNTH103-CIDP-301
Confidential 22
8. Diagnosis of SLE or family history of SLE (defined as a parent, sibling, or child).
9. Diagnosis of an autoimmune disorder other than CIDP. Exceptions (except SLE) may be granted
following Medical Monitor review and approval on a case-by-case basis.
10. Any coexisting or overlapping condition, which may interfere with outcome assessments, such as severe
diabetic neuropathy, fibromyalgia, inflammatory arthritis or osteoarthritis affecting the hands and feet
(among others).
11. Prior history (at any time) of N. meningitidis infection.
12. History of active malignancy within 5 years prior to Screening, except basal cell carcinoma of the skin,
curatively resected squamous cell carcinoma of the skin, cervical carcinoma in situ curatively treated or
low-grade prostate adenocarcinoma for which appropriate management is observation alone.
13. History of hospitalization for 24 hours or longer within the 6 weeks (42 days) prior to Part A Day 1
unless discussed with the Medical Monitor.
14. Poorly controlled diabetes (HbA1c > 7%)
15. Clinically significant drug or alcohol abuse in the opinion of the Investigator.
16. Known hypersensitivity to any of the study treatment ingredients or other therapeutic proteins.
17. Females who are breastfeeding or planning to breastfeed at any time during the study.
Laboratory Values
18. Positive test results for active human immunodeficiency virus (HIV-1 or HIV-2), hepatitis B surface
antigen (HBsAg), or hepatitis C virus (HCV) antibodies during Screening. Participants who have no
evidence of cirrhosis, have completed a curative intent regimen for HCV, and are deemed by a
gastroenterologist to have no active HCV will not be excluded.
19. Liver test results elevated more than 2-fold above the upper limit of normal (ULN) for gamma‑glutamyl
transferase (GGT), bilirubin (total), Aspartate aminotransferase (AST), or alanine aminotransferase
(ALT), unless a diagnosis of Gilbert syndrome. For the history of Gilbert syndrome, the limit is
extended to 3-fold above the ULN.
20. For female participants of childbearing potential, a positive serum pregnancy test during Screening or a
positive urine pregnancy test (with confirmatory serum pregnancy test) on Part A Day 1.
21. An ANA titer ≥ 1:320, or positive for both ANA (any titer) and double-stranded DNA (dsDNA), at
Screening. If participants have these laboratory values after recent Ig treatment, they may be retested
following discussion and agreement between the Investigator and the Medical Monitor to determine the
appropriate retesting timeframe. Retesting may require rescreening.
Medications/ Prior Treatments
22. Concurrent or previous use of the following medications within the time periods specified below:
a. Any anti-CD20 therapy within 6 months (180 days) prior to Part A Day 1.
b. PLEX within 3 months (12 weeks) prior to Part A Day 1.
c. Immunosuppressants/immunomodulatory medications (eg, azathioprine, cyclosporine,
mycophenolate mofetil, cyclophosphamide, methotrexate) within 3 months (12 weeks) prior to
Part A Day 1 except as noted for refractory treatment condition (See Inclusion 9.c).
d. If using any other current or prior medications for treatment of CIDP or that could affect immune
function, the Investigator must consult the Medical Monitor to determine appropriate washout
periods (if applicable) prior to Part A Day 1.
23. Currently or previously on complement inhibitors.
24. Currently on anti-neonatal Fc receptor (FcRN) agents. Participants who were previously on anti-FcRN
agents and took their last dose at least 5 half-lives or 90 days, whichever is greater, prior to Part A Day 1
may be considered after review and approval by the Medical Monitor.
25. Participation in another clinical trial of an investigational drug within 90 days or 5 half-lives of the
investigational agent (whichever is longer) prior to Part A Day 1.
26. Receipt of any live vaccine within 30 days prior to Part A Day 1 or expected to receive a live vaccine
during the study