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Data Safety Monitoring Board Charter (OBX319-301)

Document ID: TMF-004
Version: 1.0
Change History: 1.0 — Initial issue.
Standard(s): ICH E6(R3) / E9

Data Safety Monitoring Board Charter — OBX319-301

Establishes the independent DSMB for OBX319-301: composition, responsibilities, meeting schedule, the accumulating-safety-data review process, unblinding conventions, and recommendation pathways to the sponsor. The DSMB safeguards subject safety and trial integrity. FDA DMC guidance; ICH E6(R3)/E9.

OBX319-301 is a Phase 3, randomized, double-blind, placebo-controlled trial evaluating OBX-319, an anti-CD19 x anti-CD20 B-cell-depleting bispecific monoclonal antibody (humanized IgG1, produced in Chinese Hamster Ovary [CHO] cell culture, administered subcutaneously) on a background of standard-of-care in adults with moderate-to-severe active Systemic Lupus Erythematosus (SLE). Because OBX-319 acts by profound and durable depletion of the peripheral CD19+/CD20+ B-cell compartment, the anticipated risk profile is dominated by the recognized consequences of B-cell depletion — serious and opportunistic infection and hypogammaglobulinaemia — together with administration (injection) reactions and immunogenicity. This Charter is written to ensure that these class-defining risks are monitored with the specificity and rigor a Phase 3 immunology programme requires. The Charter is the controlling governance document for the DSMB and takes precedence over informal practice; where it is silent, ICH E6(R3), ICH E9, and prevailing FDA data monitoring committee guidance govern.

1. Purpose and Scope

The DSMB is a group of independent experts, external to the sponsor and to the participating investigators, charged with periodically reviewing accumulating safety data from OBX319-301 to protect the interests of enrolled subjects and to preserve the scientific validity and integrity of the trial. The DSMB advises the sponsor on whether the trial should continue as designed, continue with modification, pause enrollment or dosing, or be terminated for safety reasons.

The DSMB's remit is confined to OBX319-301. It does not conduct the trial, does not perform site management, does not adjudicate individual efficacy endpoints (adjudication of clinical endpoints, where required, is performed by a separate blinded committee under its own charter), and does not assume the sponsor's regulatory reporting obligations. The DSMB is advisory; final decisions on trial conduct rest with the sponsor, Virtual Biopharma Inc., which will document its rationale whenever it does not adopt a DSMB recommendation.

2. Trial Design Elements Relevant to Safety Monitoring

The DSMB's review is framed by the following design features, which determine the exposure being monitored and the comparator against which safety signals are judged:

• Design: randomized, double-blind, placebo-controlled, three-arm, 1:1:1 allocation.
• Planned enrollment: approximately 480 subjects randomized to high-dose OBX-319, low-dose OBX-319, or placebo, all on background standard-of-care.
• Population: adults with moderate-to-severe active SLE, with a baseline SLEDAI-2K of approximately 11 reflecting active disease at entry.
• Treatment duration: a 52-week double-blind treatment period, providing sustained exposure over which the durability of B-cell depletion and its downstream immunologic consequences develop.
• Route: subcutaneous administration, relevant to the monitoring of injection reactions and administration-associated systemic reactions.
• Primary endpoint (for context only): SRI-4 response with attainment of low disease activity (SLEDAI-2K ≤ 4) at Week 52. The DSMB is a safety body and does not review or interpret primary efficacy results except insofar as futility or benefit-risk considerations bear on subject safety.

The comparator structure is important to the DSMB's task: because two active dose levels and a placebo arm accumulate in parallel, the DSMB is positioned to detect not only absolute event rates but dose-related and active-versus-placebo differences in infection, immunoglobulin depletion, and administration reactions.

3. DSMB Composition and Independence

The DSMB comprises voting members selected for expertise appropriate to the population, the modality, and the anticipated risks. Minimum composition:

• A rheumatologist / SLE clinician with experience managing moderate-to-severe lupus and its therapies.
• An infectious-diseases physician, given that serious and opportunistic infection is the principal identified risk of B-cell depletion.
• A clinical immunologist familiar with humoral immunodeficiency, hypogammaglobulinaemia, and the immunologic consequences of sustained B-cell depletion.
• An independent biostatistician experienced in the sequential review of accumulating safety data.

A member is designated Chair. The Chair leads meetings, is the primary point of contact with the sponsor for DSMB matters, and is responsible for ensuring recommendations are communicated accurately. All voting members are independent of the sponsor and of the trial sites: they hold no role in trial conduct, are not investigators, and have no direct financial interest in the outcome. Members serve for the duration of the trial; a replacement of comparable expertise is appointed if a member withdraws, and the transition is documented.

4. Conflict of Interest and Confidentiality

Each member discloses financial and non-financial interests before appointment and updates disclosures if circumstances change. Members must not hold equity in Virtual Biopharma Inc., must not be participating investigators, and must not have consulting relationships that a reasonable observer would view as compromising independence. Disclosures are retained in the Trial Master File.

Comparative (unblinded) safety data, closed-session discussions, and DSMB deliberations are strictly confidential. Members must not disclose interim comparative results — by treatment arm or by dose — to the sponsor's study team, investigators, subjects, or any party who could act on them, because premature disclosure could bias trial conduct, differential reporting, or subject management. Confidentiality obligations survive the trial.

5. DSMB Responsibilities

The DSMB:

1. Reviews accumulating safety data at scheduled and, if needed, ad hoc intervals.
2. Evaluates the overall benefit-risk balance as it evolves, with particular attention to the modality-specific risks in Section 6.
3. Monitors the rate and severity of serious adverse events, deaths, and events of special interest, by treatment arm and by dose.
4. Assesses whether protocol-defined risk mitigations (screening exclusions, infection surveillance, immunoglobulin monitoring, dosing pause/discontinuation rules) are functioning as intended.
5. Recommends continuation, modification, temporary suspension, or termination of the trial, or of an individual dose arm, on safety grounds.
6. Reviews any substantive protocol amendment with safety implications and any new external safety information relevant to the class or the molecule.
7. Documents its recommendations and the basis for them.

6. Safety Parameters and Events of Special Interest

Monitoring is deliberately weighted toward the consequences of B-cell depletion by a CD19 x CD20 bispecific antibody. The DSMB gives focused attention to the following, reviewed by arm and by dose and, where informative, against placebo:

• Serious and opportunistic infection. The principal identified risk. The DSMB tracks the incidence, severity, site, and causative organism of serious infections, and specifically surveys for opportunistic and reactivation events (including hepatitis B reactivation, tuberculosis, Pneumocystis jirovecii pneumonia, and progressive multifocal leukoencephalopathy). Screening exclusions and prophylaxis/monitoring requirements in the protocol are reviewed for adequacy.
• Hypogammaglobulinaemia and prolonged B-cell depletion. Serial serum immunoglobulins (IgG, IgM, IgA) and the depth and duration of CD19+ B-cell depletion are monitored. The pharmacodynamic expectation is near-complete peripheral depletion on both active arms (from approximately 210 to approximately 7 cells/µL), with placebo essentially unchanged; the DSMB evaluates whether the observed depletion, and the trajectory of immunoglobulin decline and recovery, are consistent with acceptable risk, and whether persistent hypogammaglobulinaemia warrants intervention thresholds.
• Administration (injection) reactions and hypersensitivity. Given subcutaneous dosing and B-cell engagement by a bispecific antibody, injection-site reactions and systemic administration-associated reactions (including cytokine-release–type and hypersensitivity reactions, particularly around initial exposures) are monitored, together with the adequacy of first-dose observation and management provisions.
• Immunogenicity / anti-drug antibodies (ADA). Because immunogenicity is relevant for this modality, the DSMB is apprised of emerging ADA and neutralizing-antibody data insofar as they bear on safety — for example, associations between ADA and administration reactions, loss of pharmacodynamic effect, or altered exposure under target-mediated drug disposition (TMDD) pharmacokinetics.
• Haematologic effects. Neutropenia and other cytopenias are tracked, as these may accompany B-cell–directed therapy and may compound infection risk.
• Deaths and other serious adverse events, regardless of causality, with narrative-level review of each death.

Certain toxicities are not expected for this molecule and are not the focus of DSMB monitoring: there is no thyroid-related boxed-warning risk (a consideration for other therapeutic classes, not for a B-cell-depleting antibody), and — consistent with the nonclinical programme for a monoclonal antibody under ICH S6(R1) — genotoxicity, carcinogenicity, and QT/hERG signals are not anticipated safety domains for this agent. The DSMB nonetheless remains alert to any unexpected signal, whether or not predicted by the nonclinical package.

7. Meeting Schedule and Formats

Organizational meeting. Before the first subject is exposed, the DSMB convenes to review and adopt this Charter, the protocol, the anticipated risk profile, the statistical monitoring approach, and the format of the data reports it will receive.

Periodic safety reviews. The DSMB meets on a regular cadence (nominally every three to six months) throughout the 52-week treatment period, with the interval adjusted to the pace of enrollment and exposure. Reviews are timed so that the DSMB sees meaningful accumulating exposure, including at least one review after approximately half of the planned 480 subjects have been randomized and have accrued interpretable follow-up.

Ad hoc meetings. The Chair may convene the DSMB at any time — including on request of the sponsor's medical monitor — to evaluate an emerging safety signal, a cluster of serious infections, a fatal event, or new external information about the class or the molecule.

Each meeting is structured in up to three parts:

• Open session — sponsor representatives and the DSMB discuss trial conduct, enrollment, protocol deviations, and blinded aggregate data.
• Closed session — DSMB members and the independent statistician only, reviewing unblinded, arm- and dose-specific comparative safety data.
• Executive session — voting members only, to formulate recommendations.

8. Data Flow and Preparation of DSMB Reports

An independent statistician (and supporting unblinded reporting group), organizationally separate from the sponsor's blinded study team, prepares the closed-session reports. This unblinded group has access to randomization/treatment assignment and produces the comparative tables the DSMB reviews; it does not participate in trial conduct and does not convey comparative results to the blinded team.

Reports are provided to members sufficiently in advance of each meeting to allow review, and include: subject disposition and exposure by arm; deaths; serious adverse events; events of special interest per Section 6 (serious/opportunistic infections, hypogammaglobulinaemia and immunoglobulin trends, B-cell depletion pharmacodynamics, administration reactions, immunogenicity-associated events, cytopenias); relevant laboratory trajectories; and listings of narrative-level events. The format is agreed at the organizational meeting and may be refined as the safety picture matures.

9. Statistical Considerations and Cumulative Safety Review

Consistent with ICH E9, the DSMB's evaluation of accumulating data is primarily a clinical judgment informed by descriptive comparisons, not a mechanical application of hypothesis tests. The independent statistician presents event rates and immunologic trajectories by arm and by dose with appropriate measures of uncertainty, and highlights dose-ordered patterns (high-dose versus low-dose versus placebo) that may indicate a treatment-related effect.

Because repeated examination of accumulating data is planned, the statistical approach is chosen so that safety monitoring does not, of itself, distort the interpretation of the trial's primary analysis; efficacy interim inference, if any, is governed by the protocol's statistical analysis plan, and the DSMB's safety reviews are conducted with that plan in view. The DSMB may request additional analyses, subgroup breakdowns, or extended follow-up of specific events at any meeting.

10. Stopping and Risk-Threshold Guidelines

Stopping guidelines are advisory aids to judgment, not automatic rules. The DSMB will give particular consideration to recommending suspension or termination of the trial, or of an individual active dose arm, where the accumulating data show, for example:

• an excess of serious or opportunistic infections on active treatment relative to placebo that is not adequately mitigated by protocol measures;
• severe or clinically consequential hypogammaglobulinaemia, or a pattern of immunoglobulin decline, that outweighs anticipated benefit;
• serious or life-threatening administration or hypersensitivity reactions;
• any unexpected serious safety signal that materially shifts the benefit-risk balance.

In each case the DSMB weighs severity, reversibility, dose relationship, biological plausibility, and the adequacy of mitigation, and may recommend continuation with enhanced monitoring or protocol modification rather than termination where that better serves subject safety.

11. Unblinding Conventions

The trial is double-blind. To preserve integrity, unblinded comparative data are confined to the closed and executive sessions and to the independent unblinded reporting group. DSMB members receive treatment assignments identified by arm (and dose) as needed to interpret safety, but this information is not transmitted to the sponsor's blinded team, investigators, or subjects.

Individual-subject emergency unblinding for clinical management is handled through the protocol's separate emergency-unblinding procedure at the site and does not require DSMB action. The DSMB itself will recommend broader unblinding only when necessary to protect subjects or when the trial is stopped.

12. Recommendation Pathways to the Sponsor

After each review the DSMB issues one of the following recommendations to a designated senior sponsor representative who is otherwise insulated from unblinded data:

• continue the trial as designed;
• continue with modification (for example, enhanced infection surveillance, additional immunoglobulin monitoring, revised eligibility, or altered dosing for an arm);
• temporarily suspend enrollment and/or dosing pending further review;
• terminate an individual dose arm; or
• terminate the trial.

Recommendations are transmitted in writing, ordinarily without disclosing the underlying comparative data that supported them. The sponsor acknowledges receipt, decides on and documents the action taken, and — where a recommendation is not adopted — records its rationale. Recommendations bearing on subject safety are acted upon without undue delay.

13. Communication and Documentation

Minutes are prepared for each meeting in two parts: open-session minutes, which may be shared with the sponsor, and closed/executive-session minutes containing confidential comparative data, which are held separately and released only under defined conditions (for example, after final database lock and unblinding). All recommendations, the sponsor's responses, member disclosures, and Charter versions are retained in the Trial Master File.

The DSMB does not communicate directly with regulatory authorities; the sponsor retains responsibility for expedited safety reporting and for informing authorities and ethics committees of DSMB-driven changes to trial conduct, consistent with applicable regulations.

14. Charter Amendments and Approval

This Charter may be amended by agreement of the DSMB and the sponsor; each amendment is version-controlled and recorded in the Change History above, with the reason for change. Amendments do not apply retroactively to completed reviews. The Charter is effective upon signature by the DSMB Chair and the sponsor's authorized representative, and its adoption is confirmed at the organizational meeting before first subject exposure.

Approval

Role	Name / Title	Signature	Date
DSMB Chair
Independent Statistician
Sponsor Authorized Representative (Virtual Biopharma Inc.)

References: FDA guidance on the establishment and operation of clinical trial data monitoring committees; ICH E6(R3); ICH E9.