Open mitochondrial research · Plain-language explainer

Published on Zenodo · October 15, 2026

Endpoint Retention in Public POLG Deoxycytidine-Deoxythymidine Trial Reports

Friedl, Andrew

Abstract

**Background:** POLG-related disease is caused by pathogenic variants in the gene encoding DNA polymerase gamma, but a clinical endpoint story cannot be inferred merely because several public endpoints move in a favorable direction. Public deoxycytidine/deoxythymidine reports now include a 2024 six-month interim POLG trial report and a 2026 longer-term report from the same trial family, creating a specific endpoint-retention problem rather than a generic mitochondrial-treatment question.

**Objective:** The selected question was whether longitudinal Newcastle Mitochondrial Disease Scale (NMDS), growth differentiation factor 15 (GDF-15) and quality-of-life endpoints in public POLG deoxycytidine/deoxythymidine reports support sustained endpoint concordance, or whether deaths, withdrawals, missing biomarker windows and single-arm cohort overlap make concordance non-identifiable.

**Methods:** Complete public primary texts and indexed primary records were inspected for two POLG dC/dT trial-family reports, two POLG-relevant preclinical nucleoside sources, one non-POLG/non-TK2 dC/dT clinical report and one 2026 POLG biomarker cohort. A source-comparison pilot coded endpoint class, follow-up window, denominator or event caveat and claim boundary. No patient-level data, private platform inputs, pooled effect size, treatment ranking, survival model or clinical recommendation was generated.

**Results:** Six public endpoint rows from two overlapping POLG trial-family reports were coded across NMDS, GDF-15, EEG and quality-of-life classes; five rows had favorable reported directions and four rows were retention- or measurement-limited. The 2024 first-ten report recorded NMDS and GDF-15 improvement over six months, while the 2026 expanded report recorded 25 starters, five deaths, five withdrawals, improved NMDS through reported windows, early GDF-15 improvement and quality-of-life improvement at selected timepoints. The same evidence also preserved open-label single-arm design, cohort overlap, changing timepoint support, missing GDF-15 windows and upper-limit biomarker constraints. Preclinical nucleoside studies supported biological plausibility and endpoint-transfer caution, not clinical rescue.

**Conclusions:** Public POLG dC/dT reports support endpoint-specific favorable signals under important retention conditions, not a demonstrated same-participant concordant clinical rescue claim. The analysis is non-causal, non-pooled and hypothesis-generating: future POLG dC/dT interpretation should require matched participant/time windows, event and withdrawal accounting, biomarker censoring rules, genotype/onset strata and comparator or natural-history anchoring before endpoint concordance is treated as identifiable.

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DOI: 10.5281/zenodo.23401702

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The paper at a glance

The question

POLG is a gene needed for mitochondrial DNA copying. Public trial reports for deoxycytidine/deoxythymidine are important, but rare-disease studies can be hard to interpret when people die, withdraw or miss testing windows.

Main takeaway

Most reported endpoint directions were favorable. The same reports also recorded deaths, withdrawals, missing biomarker windows and changing follow-up counts.

Important caution

The paper does not show that the treatment works, does not estimate survival benefit, and does not provide advice for any patient.

Why this matters

POLG is a gene needed for mitochondrial DNA copying. Public trial reports for deoxycytidine/deoxythymidine are important, but rare-disease studies can be hard to interpret when people die, withdraw or miss testing windows.

How the research was done

The paper studied public reports from people with POLG-related disease who received deoxycytidine/deoxythymidine, plus cell studies that explain why the treatment idea is biologically plausible.

What the researchers found

Most reported endpoint directions were favorable. The same reports also recorded deaths, withdrawals, missing biomarker windows and changing follow-up counts.

What this does not prove

The paper does not show that the treatment works, does not estimate survival benefit, and does not provide advice for any patient.

What researchers should test next

Future reports should show matched participant timelines, event handling, biomarker limits, genotype groups and comparison logic before claiming endpoint concordance.

Helpful definitions

Key terms in plain English

MitochondriaStructures inside cells that convert fuel into energy the cell can use.

See the evidence

Visual findings

Visual finding 1. Analysis-process figure
Visual finding 2. Concept-summary figure

For non-specialists

What this could mean for patients and families

For patients and families, the main message is cautious. The public reports are encouraging enough to justify careful follow-up research, but this paper does not turn them into treatment advice.

  • Were the same people measured at each timepoint?
  • How were deaths and withdrawals counted in endpoint summaries?
  • Were GDF-15 values missing or above assay limits?
  • Is there a comparator or natural-history anchor?
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