FOXO4-DRI

1 Identity

Retro-inverso all-D-amino-acid peptide — a FOXO4 Forkhead-domain-derived sequence fused to a cell-penetrating sequence. "Proxofim" — a name used commercially and not an approved drug name — and FOXO4-p53 interfering peptide. No CAS number is stated, because none is confirmed.

Sequence

Not stated, and the omission is deliberate. The exact published sequence, molecular formula and CAS are not confirmed against the primary paper, and this catalog will not supply from memory a residue string it does not hold. What IS established about the architecture, and is sufficient to assign the panel: the article is a retro-inverso peptide — the parent sequence reversed and rebuilt entirely from D-amino acids — derived from the FOXO4 Forkhead domain and fused to a cell-penetrating sequence. Every chiral residue is D. The construct is therefore squarely P3, and the chiral method is not an addition to its specification but the whole of its identity. Because the panel follows from the architecture rather than from the residue list, the chiral requirement is specified in full before the identity question is answered.

Molecular formula

Not established. No formula is asserted, because a formula computed from an unconfirmed residue string would be an authoritative-looking number with nothing behind it.

Average mass

Not established, and no number is printed. The arithmetic point that matters more than the number: a D-retro-inverso peptide contains exactly the same residues in the same quantity as its L-parent, merely reversed and inverted, so it has the same molecular formula and the same average and monoisotopic mass as the ordinary L-peptide of the reversed sequence. Mass spectrometry is therefore blind to the property that defines this article. Even when the sequence is fixed and the mass computed, that mass will not distinguish the intended all-D retro-inverso construct from the corresponding all-L peptide — which is the cheapest possible substitution, since L-amino acid building blocks cost a fraction of D.

Monoisotopic mass

Not established, and the same argument applies with more force. Accurate mass, however tight the tolerance, cannot distinguish a D-residue from an L-residue, and MS/MS sequencing cannot either — the fragment-ion series of an all-D peptide is identical to that of its all-L counterpart. On this article the entire identity burden falls on chiral amino-acid analysis, and a certificate showing a 5 ppm accurate mass and full MS/MS coverage has established the composition and the residue order while establishing nothing whatever about the article's defining feature.

Salt / variant note

The variant set here is stereochemical, and it is invisible to every method except one. (1) the all-L peptide of the same reversed sequence — identical formula, identical average mass, identical monoisotopic mass, identical MS/MS fragment series, and made from building blocks that cost a fraction of the D-amino acids. This is the substitution the article's economics invite, and no mass-based method detects it. (2) partial racemization: a lot in which some fraction of positions is L rather than D is likewise isobaric, and appears in a chiral analysis as a percentage rather than as a pass or a fail — which is why the specification must state a per-residue L-content limit and not merely "D-configuration confirmed". (3) The ordinary L-parent peptide read in the FORWARD direction, which is a different sequence but the same residue composition and therefore also isobaric. (4) Truncated or deletion constructs missing part of the cell-penetrating sequence, which do shift mass and are the one variant class that arithmetic catches. (5) "Proxofim" and other trade names, which denote no defined specification and confer no regulatory status.

2 Class & testing panel

Form

Single article

Testing panel

P3 — panel definition

3 Primary sources & evidence

The index reports the design and provenance of the literature, not a conclusion about effect.

Study types and identifiers only. The literature is remarkably small: ten records in total for the compound as a senolytic. Founding work, in vitro and mouse: Baar, Brandt, Putavet and colleagues, Cell 2017;169(1):132-147.e16, PMID 28340339, DOI 10.1016/j.cell.2017.02.031. Animal, aged mice: Zhang and colleagues, Aging (Albany NY) 2020, PMID 31959736. In vitro, human cells: Huang and colleagues, Front Bioeng Biotechnol 2021, PMID 33996787. In vitro: Kong and colleagues, Commun Biol 2025, PMID 39994346. In vitro structural biology: Bourgeois and colleagues, Nat Commun 2025, PMID 40593617. Reviews: Alameen and colleagues, Naunyn Schmiedebergs Arch Pharmacol 2026, PMID 42024235; Mateescu and colleagues, Antioxidants (Basel) 2026, PMID 42510573. NO human study of any kind has ever been conducted — no registered interventional trial exists, and a ClinicalTrials.gov query covering FOXO4 returns no interventional trials of the peptide. One animal report contradicting the founding work is on file at PMID 36515093; safety literature for this article is tracked under regulatory monitoring rather than restated in a product record.

4 Storage & specification

Storage

Lyophilized powder at -20 degrees C or below, desiccated, protected from light; the acetate salt is preferred and is specified on the purchase order. One point specific to the architecture: an all-D backbone is resistant to the proteolytic degradation that dominates handling risk for ordinary peptides, so the practical stability concerns are chemical rather than enzymatic — oxidation, deamidation and moisture uptake — and none of them is relieved by the D-configuration.

Shelf life

Every lot is dated from the date of QA release and carries a printed retest date, and first-expiry-first-out is enforced against that printed date. The protocol assignment for a lyophilized synthetic peptide is a provisional 24 months at -20 degrees C, and on this article it is confirmed against the residue list before it is printed, because the degradation pathways a stability-indicating method must resolve are functions of which residues are present. The attribute that limits the interval is the chiral profile: the stability program re-measures it at every pull, because epimerization over shelf life is the degradation route the purity chromatogram will not show. The interval is shortened on data and never extended without a completed dataset.