Module 3 — Control Strategy & Specifications (TILA-278)

Chemistry, manufacturing and controls document for TILA-278.

Change History

3.2 Control Strategy and Specifications — TILA-278 (Module 3 Quality Overall Summary Cross-Reference: 2.3.S / 2.3.P)

1. Introduction and Scope

This section presents the integrated control strategy and the drug-substance (DS) and drug-product (DP) specifications for TILA-278, a recombinant humanized IgG1 bispecific monoclonal antibody administered subcutaneously (SC) for the treatment of moderate-to-severe ulcerative colitis (UC). One antigen-binding arm is an antagonist of TL1A (TNFSF15); the second arm is an agonist of the interleukin-22 receptor (IL-22R, the IL-22RA1/IL-10RB heterodimer). The two functionalities are complementary: TL1A antagonism dampens TH1/TH17-driven mucosal inflammation and intestinal fibrosis, while IL-22R agonism drives epithelial regeneration and mucosal-barrier repair.

Because TILA-278 exerts two independent, mechanistically distinct pharmacologic activities from a single molecular entity, the control strategy is designed to assure that (i) each functional arm is present, correctly assembled, and biologically active; (ii) the correct heterodimeric (bispecific) species predominates over product-related mispaired variants; and (iii) product-, process-, and safety-related attributes are maintained within ranges qualified by nonclinical and clinical experience — in particular by the material used in the pivotal induction study TILA278-201.

The control strategy and specifications are established in accordance with ICH Q6B (specifications and acceptance criteria for biotechnological/biological products), ICH Q8(R2), Q9(R1), Q10 and Q11 (pharmaceutical/biotech development, quality risk management, quality systems, and DS development and manufacture), and ICH Q14 together with Q2(R2) (analytical procedure development and validation). Attribute risk ranking follows the enhanced (QbD) principles of Q8/Q9; the resulting Critical Quality Attributes (CQAs) are controlled by an integrated combination of the manufacturing process, in-process controls (IPCs), characterization testing, and release/stability specifications.

2. Elements of the Integrated Control Strategy

Consistent with ICH Q10, the control strategy for TILA-278 is not synonymous with the release specification. Assurance of quality is distributed across multiple, mutually reinforcing layers, with release testing constituting the final confirmatory layer rather than the sole control point:

• Raw-material and cell-substrate control — qualified CHO master and working cell banks (MCB/WCB), characterized per ICH Q5A(R2)/Q5B/Q5D; controlled, compendial or internally qualified raw materials.
• Upstream and downstream process control — validated fermentation and Protein A capture, polishing chromatography, and orthogonal viral-clearance steps operated within established parameter ranges (see §3).
• In-process controls and hold-time limits — IPCs at defined process points (e.g., post-capture bioburden/endotoxin, pool titer, aggregate content) with acceptance limits and validated in-process hold times.
• Attribute-based control — DS and DP release specifications plus stability specifications (this section).
• Extended characterization and comparability — orthogonal physicochemical and functional characterization supporting attribute criticality assignment and lifecycle comparability (ICH Q5E).
• Facility, sterility assurance, and container-closure control — GMP controls, aseptic processing validation, and container-closure integrity for the sterile DP.

2.1 Quality Target Product Profile (QTPP)

The QTPP anchors CQA identification and specification setting.

2.2 Critical Quality Attribute Identification and Risk Ranking

CQAs were identified via a structured quality risk assessment (ICH Q9(R1)) that scored each candidate attribute for its potential impact on safety (including immunogenicity), efficacy/potency, pharmacokinetics/exposure, and detectability/uncertainty. Attributes were ranked High/Medium/Low criticality; all High and selected Medium attributes are subject to specification and/or dedicated in-process control.

2.3 Linkage of CQAs to CPPs and In-Process Controls

The following linkage table summarizes, at the level of detail appropriate to this control-strategy overview, how each principal CQA is assured through Critical Process Parameters (CPPs), IPCs, and release testing. Detailed process descriptions and proven acceptable ranges reside in 3.2.S.2.2–3.2.S.2.4 and 3.2.P.3.3–3.2.P.3.5.

2.4 Bispecific-Specific Considerations

The obligate heterodimeric format introduces product-related species not present for a conventional monospecific mAb — homodimers of each arm, half-antibodies, and light-chain–mispaired species. Because such species can carry only one (or neither) functionality, they are simultaneously purity impurities and potency-relevant variants, and, being non-native assemblies, are treated as potential immunogenicity contributors. Correct-pairing fidelity is engineered into the molecule (heterodimerization-promoting Fc design with cognate light-chain pairing) and is controlled by the downstream polishing train; it is verified at release by intact and subunit mass spectrometry and by a resolving orthogonal method (hydrophobic-interaction chromatography, HIC). This attribute is designated High criticality and is a defining feature of the TILA-278 control strategy.

3. Drug Substance Specification (3.2.S.4.1)

TILA-278 drug substance is a recombinant humanized IgG1 bispecific antibody expressed in CHO cells and purified by Protein A affinity capture, orthogonal polishing chromatography, and dedicated viral-clearance operations (low-pH inactivation and nanofiltration), followed by ultrafiltration/diafiltration into the DS formulation and concentration. The specification comprises identity, potency (both mechanisms), purity/product-related impurities, process-related impurities, and general/safety tests.

3.1 Justification of the Drug Substance Specification (3.2.S.4.5)

Acceptance criteria were established from the combination of (i) manufacturing capability across clinical and process-consistency lots, (ii) results for the lots deployed in TILA278-201, and (iii) attribute criticality per §2.2. For High-criticality attributes with a demonstrated or plausible impact on safety, immunogenicity, or dual potency, criteria are set to bracket qualified experience; for attributes classified Medium or lower, criteria are set to assure consistency (process capability) and are reported where a clinically meaningful range has not yet been narrowed.

• Potency (both mechanisms). The dual potency limits are the pivotal justification element: because efficacy in TILA278-201 was dose-ordered — Week-12 clinical remission of 37.3% (High), 16.2% (Low), and 0.7% (placebo), with LS-mean modified-Mayo differences vs placebo of −2.36 (High; 95% CI −2.49, −2.23; p<0.0001) and −1.77 (Low; 95% CI −1.90, −1.64; p<0.0001) — the delivered biological activity of each arm is directly linked to clinical benefit. The 80–125% (TL1A neutralization) and 70–130% (IL-22R agonism) relative-potency ranges bracket the activities of the qualified clinical material and are consistent with assay format and variability (see §7). Separate acceptance criteria for each mechanism ensure that neither activity can drift out of range while the other compensates.
• Correct heterodimer / mispaired species. The ≥90% heterodimer and ≤5% mispaired limits are justified by the levels present in the toxicology and clinical lots and by the requirement that both functional arms be co-delivered on a single molecule; mispaired species reduce effective bivalent-bispecific potency and represent a non-native assembly with theoretical immunogenic potential.
• Aggregates (HMW). The ≤2.5% limit reflects both process capability and the recognized association of aggregates with immunogenicity risk for SC biologics; the limit does not exceed the levels qualified in nonclinical (cynomolgus repeat-dose SC) and clinical use.
• Charge and glycan variants. Limits are supported by characterization showing that acidic/basic and glycoform distributions across this range have no meaningful impact on either binding activity, FcRn-mediated PK, or Fc effector engagement. Afucosylation and high-mannose are controlled because they modulate FcγRIIIa binding and clearance; as the therapeutic mechanism is neutralization/agonism rather than effector-mediated killing, effector function is monitored as a characterized attribute rather than a potency driver.
• Process-related impurities (HCP, DNA, Protein A). Limits conform to established safety expectations for parenteral biologics and are supported by validated downstream clearance and IPC data; residual DNA is well below the WHO/ICH health-based threshold at the maximum clinical dose.
• Safety/general tests. Endotoxin and bioburden limits are set to protect the sterile DP and are consistent with compendial requirements.

4. Drug Product Specification (3.2.P.5.1)

TILA-278 drug product is a sterile, preservative-free solution presented in a single-use prefilled syringe and an autoinjector incorporating the same primary container. The formulation comprises an aqueous buffer system with polysorbate as surfactant, at the nominal protein concentration and fill defined in the QTPP.

4.1 Justification of the Drug Product Specification (3.2.P.5.6)

DP acceptance criteria follow the DS rationale, adjusted to include DP-specific fill/finish and device attributes and to accommodate the incremental change in size-variant and particulate attributes that can occur across fill/finish, storage, and device actuation. Purity limits are set marginally wider than DS (e.g., HMW ≤3.0% at DP vs ≤2.5% at DS) to account for fill/finish and shelf-life change while remaining within the ranges qualified in TILA278-201; the DP potency ranges are held identical to DS to preserve the clinical link established by the dose-ordered efficacy above. Where release and end-of-shelf-life behavior differ (principally aggregate and charge-variant content), distinct release and shelf-life acceptance criteria are applied and are supported by the stability data underpinning the assigned shelf life.

• Particulate matter and immunogenicity. For an SC biologic, subvisible particulate limits are conservative and compendial, reflecting the immunogenicity-risk relevance of particulates; polysorbate is specified because interfacial protection is the primary defense against agitation- and interface-induced aggregation over shelf life.
• Deliverable dose and device function. Extractable volume, content, and device functional attributes (break-loose/glide force, injection time) assure that the intended dose is reliably delivered SC, supporting the exposure–response relationship demonstrated across the High and Low arms.
• Sterility assurance. Sterility, endotoxin, and CCIT are justified by aseptic-processing validation and container-closure integrity studies; CCIT is retained on stability in lieu of routine sterility testing per the container-closure integrity lifecycle approach.
• Clinical qualification. All release and shelf-life acceptance criteria bracket the attribute levels of the DP lots administered in TILA278-201, over which the safety profile (treatment-emergent adverse-event rates in the active arms that did not exceed placebo and showed no dose-dependent increase; injection-site reactions as the principal drug-attributable finding) and dose-ordered efficacy were established.

5. Potency Control Strategy — Dual Mechanism

Because TILA-278 has two independent pharmacologic activities, potency cannot be represented by a single assay. A two-assay potency strategy is implemented at both DS and DP release and on stability, each assay reflecting one arm's mechanism of action, complemented by characterization-level assays that confirm the two activities reside on a single molecule.

• TL1A neutralization potency. A cell-based neutralization bioassay measures the ability of TILA-278 to antagonize TL1A-mediated signaling through the DR3 receptor (e.g., inhibition of a TL1A-inducible NF-κB reporter or of TL1A-driven cellular response). Relative potency is calculated against the reference standard by parallel-line/four-parameter logistic analysis. This assay is the MoA-reflective release control for the anti-inflammatory (TH1/TH17-dampening, anti-fibrotic) arm.
• IL-22R agonist potency. A cell-based reporter-gene bioassay quantifies agonism of the IL-22RA1/IL-10RB receptor complex (STAT3-responsive reporter in an IL-22R–expressing line). Relative potency is likewise determined against the reference standard. This assay is the MoA-reflective release control for the mucosal-healing/epithelial-regeneration arm.
• Simultaneous dual-binding confirmation. A bridging binding assay (capture on one target, detection via the other) confirms that a single TILA-278 molecule engages both TL1A and IL-22R — the functional signature of correct bispecific assembly. This is used as an identity/characterization control and supports the interpretation of the two bioassays.

The dual-assay design ensures that loss of activity in either arm is independently detectable and cannot be masked. Both bioassays are stability-indicating (see §6/§7) and are the pivotal quality link to the dose-ordered clinical efficacy of TILA278-201.

6. Purity and Product-Related Impurity Control

Purity is controlled by orthogonal, mechanistically distinct methods that resolve the principal product-related variant classes:

• Size variants — SEC-HPLC (native, quantifies monomer, HMW aggregates, LMW fragments) and CE-SDS (reduced and non-reduced; covalent size heterogeneity, fragmentation, and incomplete assembly).
• Charge variants — imaged capillary isoelectric focusing (iCIEF), resolving acidic and basic species arising from deamidation, C-terminal lysine, sialylation, and related modifications.
• Assembly / pairing variants (bispecific-specific) — intact and subunit LC-MS with orthogonal HIC to quantify correctly paired heterodimer and to detect homodimers, half-antibodies, and light-chain–mispaired species.
• Glycan variants — released N-glycan mapping (HILIC-FLR/MS) for afucosylation, high-mannose, galactosylation, and sialylation.

Aggregates are given particular weight because of their recognized association with immunogenicity for SC-administered antibodies; their control spans process (culture and polishing CPPs), IPC (post-polishing pool SEC), release, and stability. Fragment and charge-variant limits are qualified by characterization demonstrating no adverse impact on the two binding activities or on FcRn-mediated exposure across the specified ranges.

7. Safety Attribute Control

Safety-relevant attributes are controlled through the layered strategy of §2:

• Process-related impurities — HCP (process-specific qualified ELISA), residual host-cell DNA (qPCR), and residual Protein A (immunoassay), each with validated downstream clearance and IPC coverage; residual DNA is below the health-based threshold at the maximum clinical dose.
• Adventitious-agent / viral safety — cell-substrate characterization per ICH Q5A(R2)/Q5D, with orthogonal viral inactivation (low-pH) and removal (nanofiltration) steps; validated clearance is summarized in 3.2.A.2. Endotoxin and bioburden are controlled at DS and DP and via IPCs.
• Sterility assurance — aseptic-processing validation, sterilizing-grade filtration with pre-/post-use integrity testing, sterility (USP <71>) at DP release, and container-closure integrity on stability.
• Elemental and other risk-assessed impurities — an elemental-impurity risk assessment (ICH Q3D) confirms that the aqueous formulation, single-use container-closure components, and manufacturing train contribute elemental impurities below the applicable parenteral permitted daily exposures, so routine elemental-impurity release testing is not warranted; a nitrosamine risk assessment covering excipients and process inputs identifies no root cause for N-nitrosamine formation in this recombinant process and formulation.
• Particulates and immunogenicity-related attributes — subvisible (USP <788>) and visible particulate control, plus surfactant (polysorbate) control, aggregate limits, and monitoring of glycation/sequence-variant risk factors, collectively constituting the physicochemical immunogenicity-risk control. These controls are consistent with the clinical immunogenicity outcome (ADA assessed by a tiered assay with evaluation of impact on PK, efficacy, and safety) and with the observed safety profile in TILA278-201, where injection-site reactions were the principal drug-attributable finding and no dose-dependent safety signal emerged.

8. Analytical Control Approach (ICH Q14 / Q2(R2))

8.1 Analytical target profiles and procedure lifecycle

Analytical procedures are developed and maintained under an ICH Q14 lifecycle framework. Each release-defining method has an Analytical Target Profile (ATP) specifying the required reportable range, accuracy, precision, specificity, and, for the potency bioassays, the relative-potency range and system-suitability/parallelism criteria. Procedures are validated per ICH Q2(R2) for the relevant characteristics (specificity, accuracy, precision/intermediate precision, linearity, range, and, where applicable, LOD/LOQ). Changes to procedures across the lifecycle are managed by pre-defined method-comparability/co-validation protocols to preserve consistency of the reportable result.

8.2 Categories of analytical procedures

• Identity — orthogonal set: the two ligand-binding identity assays, the dual-binding bridging assay, peptide mapping, intact/subunit LC-MS, and iCIEF.
• Potency — the two cell-based bioassays (§5), qualified as stability-indicating and MoA-reflective; system suitability includes reference-standard parallelism and assay-control acceptance.
• Purity/impurity — SEC-HPLC, CE-SDS (reduced/non-reduced), iCIEF, HIC, LC-MS, and N-glycan mapping.
• Process-related impurity — HCP ELISA, residual-DNA qPCR, residual Protein A immunoassay.
• General/safety — appearance, color/clarity, pH, protein concentration (A280), osmolality, polysorbate, subvisible/visible particulates, endotoxin, bioburden, sterility, CCIT, and device functional tests.

8.3 Stability-indicating capability and forced degradation

The stability-indicating nature of the control panel was established through forced-degradation studies (thermal, low/high pH, oxidative, photolytic, mechanical/agitation, and freeze–thaw stress). These studies demonstrate that SEC-HPLC, CE-SDS, iCIEF, and both potency bioassays detect and quantify the degradation pathways relevant to TILA-278, and they confirm that loss of activity in either functional arm is detected by the corresponding bioassay. Stress-induced increases in aggregate and charge-variant species correlate with the trended stability attributes, supporting the assignment of the shelf-life specification and the excursion/in-use claims.

8.4 Reference standard

A two-tiered reference-standard system is maintained: a primary reference standard, extensively characterized and traceable to clinical-qualification material (including the lots used in TILA278-201), and working reference standards qualified against the primary standard under a defined protocol. The reference standard is used to anchor identity, potency (both mechanisms), and charge/size-variant comparisons, ensuring continuity of the reportable value across the product lifecycle. Requalification and bridging of successive reference standards follow a pre-approved protocol to prevent drift in reported potency and purity.

8.5 Comparability and lifecycle management

Manufacturing changes are assessed for their impact on CQAs under an ICH Q5E comparability framework, using the release panel supplemented by extended characterization (higher-order structure, full glycan and charge-variant mapping, forced degradation, and orthogonal potency/binding methods). The control strategy, specifications, and analytical procedures are subject to continual review under the pharmaceutical quality system (ICH Q10): specification acceptance criteria and attribute-criticality assignments will be reassessed as additional manufacturing and clinical experience accrues (including confirmatory-phase data beyond the Phase 2b induction study TILA278-201), and any tightening or refinement will be justified against accumulated process capability and the established exposure–response relationship.

9. Summary

The TILA-278 control strategy is an integrated, risk-based system in which the manufacturing process, in-process controls, and DS/DP specifications jointly assure the quality attributes essential to the molecule's dual mechanism of action. Its distinguishing features are (i) a two-assay potency strategy that independently controls the anti-TL1A neutralizing and IL-22R agonist activities and links them to the dose-ordered clinical efficacy observed in TILA278-201; (ii) explicit control of correct bispecific heterodimer assembly and mispaired-species content; and (iii) conservative control of aggregates, particulates, and process-related impurities appropriate to a subcutaneously administered biologic, consistent with the favorable safety and immunogenicity profile of the pivotal study. All acceptance criteria bracket the attribute levels of nonclinically and clinically qualified material, and the analytical control approach is maintained under an ICH Q14/Q2(R2) and Q10 lifecycle framework.