DLV-2026-002 Tier 2 dossier Public excerpt - 2 of 7 sections April 2026

TPO Receptor Agonists vs FcRn Inhibitors in Immune Thrombocytopenia

Mechanistic distinction, clinical signal comparison, and the off-treatment durability gap. Indication scope: 2L+ adult chronic ITP.

Hematology Medical Affairs / MSL Phase 2-3 RCT data Mechanism analysis

Section 1 - Executive summary

Different problems, no class superiority on durability

Central thesis - council-reviewed

TPO receptor agonists and FcRn inhibitors solve different biological problems in ITP, but neither has been demonstrated to modify the underlying autoimmune disease.

TPO-RAs achieve superior on-treatment response by overcoming platelet destruction at the production level. FcRn inhibitors reduce the destruction signal (pathogenic IgG) more directly, but with lower clinical efficacy and uncharacterised off-treatment durability. The decisive clinical question - which class enables durable remission off therapy - remains open for FcRn inhibitors.

79%

Eltrombopag response RAISE Phase 3 [RCT]

22%

Efgartigimod sustained ADVANCE IV [RCT]

30%

TPO-RA off-treatment remission (TAPER) [RCT]

N/D

FcRn off-treatment durability - not published

Evidence tier system used throughout this dossier

RCTRandomised controlled trial. Highest evidence.
IndirectMechanistic inference or cross-trial comparison. No head-to-head RCT.
RWEReal-world evidence. Hypothesis-generating.
EditorialAnalytical interpretation. Not a published conclusion.

No head-to-head RCT between TPO-RAs and FcRn inhibitors exists. All cross-class comparisons in this dossier are Indirect.

1.1 Key findings at a glance

Domain	TPO-RAs	FcRn inhibitors	Verdict
Mechanism layer	Downstream - stimulates platelet production	Upstream - reduces pathogenic IgG catabolism	Different targets
On-treatment response	38-79% RCT	5-22% RCT	TPO-RA superior
Time to response	1-2 weeks RCT	7-8 days RCT	Comparable
Off-treatment remission	30-33% RCT+RWE	Not published	Data gap - FcRn
ADA formation	Minimal (oral small molecule)	Rozanolixizumab 71-75%	TPO-RA advantage
Disease modification	Not proven Editorial	Not proven Editorial	Neither class

Table 1.1 - Summary comparison. All cross-class comparisons are Indirect (no head-to-head RCT).

Section 3 - Clinical signal comparison (excerpt)

Agent-level trial data and durability asymmetry

3.1 Agent-level trial data

Agent	Class	Key trial	Primary endpoint	Response	Evidence
TPO receptor agonists
Eltrombopag	TPO-RA	RAISE (Ph 3)	≥50×10⁹/L at least once (6mo)	79% (vs 28% pbo, p<0.0001)	RCT
Eltrombopag	TPO-RA	EXTEND (Ph 3 OLE)	Continuous response ≥25w on-treatment	52%	RCT
Eltrombopag	TPO-RA	TAPER (Ph 2)	Sustained off-treatment response ≥26w	30.5%	RCT
Romiplostim	TPO-RA	Kuter 2008 (Ph 3)	Durable response ≥50×10⁹/L for ≥6/8w	38-61%* (vs 0-5% pbo)	RCT
Avatrombopag	TPO-RA	Ph 3 (NCT01438840)	Cumulative weeks ≥50×10⁹/L without rescue	65.6% at Day 8 (vs 0% pbo)	RCT
FcRn inhibitors
Efgartigimod	FcRn	ADVANCE IV (Ph 3)	Sustained ≥50×10⁹/L for ≥4 of last 6 weeks	22% (vs 5% pbo, p=0.032)	RCT
Rozanolixizumab	FcRn	TP0003 (Ph 3, terminated)	Durable ≥50×10⁹/L for ≥8/12w	19% (4/21)	RCT Underpowered
Rozanolixizumab	FcRn	TP0006 (Ph 3, terminated)	Durable ≥50×10⁹/L for ≥8/12w	5% (1/20)	RCT Underpowered
Nipocalimab	FcRn	-	-	No ITP data published	No data

*38% splenectomised, 61% non-splenectomised. Rozanolixizumab trials terminated early at 30-40% of planned enrolment - formally underpowered. All cross-class comparisons are Indirect.

3.4 Durability: the decisive asymmetry

Durability is the lens through which both classes must ultimately be judged. The data are strikingly asymmetric - not because one class is clearly superior, but because the comparison cannot yet be made.

Metric	TPO-RAs	FcRn inhibitors
On-treatment "continuous response"	52% (EXTEND, ≥25w) - on-treatment only	22% (ADVANCE IV, ≥4/6w) - on-treatment only
Off-treatment remission (published)	30.5% (TAPER, ≥26w off drug) RCT	Not published in any Phase 3 ITP trial
Relapse kinetics post-cessation	Gradual; 70% relapse within 2-4 weeks RWE	Likely rapid (IgG rebounds 3-5w post-dose); not formally measured
Re-treatment response maintained?	Yes - ~70-80% re-respond (REPEAT trial) RCT	Unknown - not studied
Data maturity	15+ years Phase 3 + RWE	<3 years Phase 3 data; OLE ongoing

Table 3.4 - Durability comparison. Off-treatment remission is the only unambiguous measure. For FcRn inhibitors, this metric is currently unpublished.

Critical gap for MSLs

When a hematologist asks "Which drug is more durable?" the honest answer for FcRn inhibitors today is: "We have robust on-treatment response data (22% sustained, ADVANCE IV), but off-treatment durability has not been formally measured in any published Phase 3 ITP trial. ADVANCE NEXT will provide this data." Claiming equivalence to TPO-RA durability without this data is scientifically unsupportable.

Not shown in this public excerpt

The full report (28 pages, 7 sections) additionally contains:

Section 2 - Mechanistic framework. Why upstream mechanism ≠ disease modification. Treg/Th17 logic. Re-baseline kinetics.
Section 4 - Endpoint and interpretation critique. Why the ≥50×10⁹/L platelet threshold conflates hemostatic rescue with disease modification. Continuous dosing bias. Underpowered Phase 3 reliability scoring. ADA formation.
Section 5 - MSL strategic positioning. Evidence-based talking points, what MSLs cannot claim without data, hematologist objection handling.
Section 6 - Forward signals. Pivotal readouts (ADVANCE NEXT, LUNA 3, Q32 ADX-097), competitive landscape, plausible label-language shifts.
Section 7 - References. Full citation list, ClinicalTrials.gov IDs, EMA/FDA label cross-references.

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DLV-2026-002 - Tier 2 dossier - April 2026.
Sources cited in this excerpt: RAISE (Cheng et al., Lancet 2011), EXTEND (Saleh et al., Blood 2013), TAPER (Provan et al., Br J Haematol 2024), Kuter 2008 (Lancet), ADVANCE IV (Broome et al., Lancet 2023), TP0003/TP0006 (Robak et al., Blood Adv 2020), ClinicalTrials.gov NCT04562766, NCT04562766, NCT01438840. Mechanistic interpretation and editorial framing are explicitly tagged.

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