PN-943

At a glance

Overview

The development concept is local intestinal activity with low systemic exposure. PN-943 binds α4β7 integrin, a target also used by an approved antibody medicine, but that shared target does not establish equivalent efficacy or safety. Healthy-volunteer studies supported oral stability and target engagement. The IDEAL phase 2 study then tested clinical remission in moderate-to-severe ulcerative colitis. Its higher-exposure primary comparison was negative, while the lower group showed a numerical signal. The sponsor subsequently prioritized other programs and stated that it would not commit further internal development resources beyond completing the extension.

Supporting sources [1] [2] [3] [4]

How it works

α4β7 integrin helps leukocytes interact with MAdCAM-1 and traffic to intestinal tissue. PN-943 is designed to inhibit that interaction and related immune-cell activation while remaining largely within the gastrointestinal compartment. Low measured plasma exposure is consistent with this design, but it does not by itself prove adequate tissue effect or absence of systemic biological consequences. Receptor occupancy is a pharmacodynamic marker, not clinical remission.

Supporting sources [1] [2] [3] [4]

What healthy-volunteer studies showed

Phase 1 studies found low systemic exposure and measurable target engagement, with generally favorable short-term tolerability. These findings supported testing in ulcerative colitis but could not establish clinical efficacy in inflamed bowel.

Supporting sources [1]

IDEAL results

The sponsor reported 159 evaluable patients. The higher trial group did not separate from placebo on the prespecified primary endpoint. The lower group had 27.5% clinical remission versus 14.5% with placebo, a numerical difference that did not reach conventional statistical significance in the overall analysis.

Supporting sources [2]

Do not substitute a predecessor study

PTG-100 is a related predecessor, not another name for PN-943. Results from PTG-100 cannot be assigned directly to PN-943. Similarly, efficacy of an approved injectable α4β7 antibody validates the target’s relevance without validating this oral molecule.

Supporting sources [1] [2]

What remains unresolved

Early tolerability and low plasma exposure do not establish long-term safety in active inflammatory bowel disease, combination therapy or pregnancy. A complete clinical benefit-risk profile would require successful confirmatory development and broader exposure.

Supporting sources [1] [2]

Program status

In its third-quarter 2022 update, Protagonist stated that it intended to dedicate no further internal clinical or manufacturing-development resources after completing the IDEAL extension. The record is therefore research history, not evidence of an approved or continuously advancing phase 3 product.

Supporting sources [3]