KIF18A in Aging

KIF18A is a kinesin-8 motor that walks toward the growing plus ends of the microtubules a dividing cell assembles into its spindle, depolymerizing those ends as it goes. By dampening the dynamics of the kinetochore-microtubules, the subset of those fibers held by the protein plate built on each chromosome, it drives the chromosomes into alignment at the metaphase plate, the movement termed congression. Loss of the protein is nonetheless compatible with life in the mouse, where animals lacking it are viable and the consequence on record falls on the germ line, sterility being reported in males of the null strain and infertility in both sexes of a strain carrying a missense substitution in the motor domain, whereas the human evidence runs the other way, in that the constraint band recorded for the gene marks it intolerant of loss of function.

The case for an inhibitor rests on that murine tolerance, and it is also the first place the evidence thins, because the genetic case is graded on a constraint band that was never checked against the underlying population database, while the safety read rests on the very mouse work that the aging argument reads in the opposite direction.

Every figure in the card above is reproduced as recorded rather than recalculated here, with identity credited to UniProt and NCBI Gene, structures to PDBe and RCSB PDB, and variants to GWAS Catalog and ClinVar. Species identity is credited to Ensembl Compara and baseline expression to the Human Protein Atlas, each accessed 2026-08-13, whereas the constraint band is credited to gnomAD and is the one figure among these for which no access date was recorded alongside the database that supplied it.

The paralog table and the stated selectivity concern

The case for selectivity rests on the five kinesin paralogs plotted above, of which the closest, KIF18B, shares 36.4 percent of its sequence with KIF18A, while the remaining four diverge further still, a separation read as sufficient for a molecule that engages one member of the family without engaging the others. A different mitotic kinesin is nonetheless identified as the selectivity concern that governs the program, and that kinesin has no row in the alignment table from which the figure is drawn.

The measured identities and the stated warning therefore concern different proteins, in that the distances above reduce selectivity within the graded family to a medicinal-chemistry problem, whereas the warning places the liability it names outside that set, in a second mitotic kinesin that a molecule aimed at this target is required to spare, because inhibiting it as well would carry back the marrow liability described above. The two statements occupy a single paragraph of the record without being reconciled, and both are carried onto this page in that condition, since choosing between them would assert more than the evidence settles.

Seven experimental structures of KIF18A have been deposited, the sharpest of which is judged suitable for structure-based design, and the site at which the inhibitors in this field are aimed is an allosteric one on the motor domain, the alpha-4 helix, rather than the nucleotide pocket every kinesin possesses.

Because the motor domain is conserved across the kinesin family even where the sequence around it diverges, selectivity against the nearest paralogs cannot be read from the KIF18A structure alone and has to be established by comparison with them, which every compound now in the clinic reports having done. Five relatives carry a measured identity to KIF18A, and KIF11 is not one of them, so the kinesin this program most needs to spare is the one those figures never measure.

KIF18A: seven listed, by X-ray crystallography and cryo-electron microscopy. A dash in the share column marks a structure for which no coverage figure was recorded, which is the case for seven of the seven entries.

Patent filings against the target

Six patent holders stand on record against this target, as of a search dated 2026-08-15 whose stated account is reproduced beneath the table in the words it was given, and the 23 filings listed against them are set out below, each attributed to its holder beside the chemical series it is recorded to cover, where the record states one. The field is judged active at source; the figures available here to set against that judgment are the six holders named in the table below and the filings, where any are recorded, listed beside each of them. Freedom to operate, the right to make and sell a compound without infringing a patent held by another party, is settled by the chemical series a program runs on rather than by the protein it aims at.

A full-text search of the patent corpus on FreePatentsOnline returns 976 patent publications that mention KIF18A, and every publication number in the table was then opened on its own record in the PubChem patent view before it was written down, both retrieved 2026-08-15, with the chemical series characterized from the disclosures themselves and from a review that compares them directly. Menarini appears in no row because a search of the same corpus returns no filing against the target in its name, a result read against a control search that returns 547 patent publications for that name alone; the compound it has taken into the clinic was originated elsewhere, and the composition-of-matter filings behind it are recorded here under the originator.

Two searches, one over ClinicalTrials.gov and one over a curated trials dataset with substantially overlapping coverage, both conducted on 2026-08-13, returned the same picture: a crowded early-stage oncology field, and nothing whatever outside it.

That constitutes the whole of the human evidence, so that every claim connecting KIF18A to aging rests ultimately on work carried out in patients with advanced cancer, and the record reads that transfer two ways, bridged inside the oncology trials on one reading and rejected as unsupported and mechanistically self-contradictory on the other.

Rows are grouped by the stage each program has reached to date, and a square marks each of the two programs that have reached the furthest stage; where anything stands on record about a program beyond its registry entry, it is printed beneath the setting.

The one trial with a reported efficacy readout

Everything set out below comes from NCT05902988, Volastra’s study of VLS-1488, whose figures were presented in abstract 3012 at the American Society of Clinical Oncology (ASCO) 2025 meeting, and that presentation is the only occasion on record on which any of these compounds has been given to patients and the resulting numbers put into the public record.

The stage, sponsor, status and enrollment field for this trial were read from the registered landscape, whereas the efficacy and safety figures in the findings column were retrieved separately and are attributed to the 2025 conference abstract named above.

Expression ranking against the clinical record

KIF18A has been scored across thirteen diseases, and the top of that ordering is set here against the clinical record. The ordering itself is not in dispute, whereas the evidential weight that ordering carries remains open, given that an expression fold change and a Phase 1 readout are not the same class of evidence, and given that the two aging entries rank lowest in the scored list.

Composite scores, fold changes and p-values are carried through unaltered, whereas the clinical column records what has reached a patient; fold changes are combined meta-analysis values on a log scale, and p-values recorded in machine exponent form are printed here in superscript notation.

Each grade is drawn on the three-step scale this page uses for confidence, and the grade the source itself recorded is stated in the basis cell beside it wherever the two do not coincide.

KIF18A has been scored across a broad field of candidate indications, and the leading entries, grouped by therapeutic area, are dominated by cancers carrying high chromosomal instability, which is precisely the population a KIF18A inhibitor is designed to kill.

Two age-related entries appear within that shortlist, only one of which carries a measured fold change of its own, and both arrive with a reliability flag attached warning that they should not be pursued on the score alone.

Differential expression in oncology and age-related indications

The largest fold change in the table is 0.520, in hepatocellular carcinoma, whereas the only age-related disease it contains is Alzheimer’s disease at 0.121, the smallest positive value the table prints, and that value is attributed to dividing glial cells rather than to any KIF18A mechanism.

Each bar is one disease’s log2 fold change, which is the base-two logarithm of the ratio between KIF18A transcript abundance in diseased tissue and its abundance in matched normal tissue, so that a positive value denotes higher abundance in the diseased state. Three of the fourteen values are negative, and each of those three belongs to a hematological malignancy.

These are the normal-tissue levels against which the fold changes are measured, and in normal tissue KIF18A behaves as a proliferation marker rather than as a broadly expressed gene, given that the three tissues carrying the most of it are the three that divide the most. Baseline abundance in normal human tissue is highest in testis, at 12.8 normalized transcripts per million (nTPM), followed by lymphoid tissue at 8.9 and bone marrow at 7.8.

Indication ranking across the two scoring runs

Every indication graded Go is a cancer, whereas the three indications graded No-go include the wider run’s two age-related entries, neurodegenerative disease and diabetes mellitus; the table carries the thirteen indications that were sorted into tiers, together with three further indications that the 1,000-indication run ranked and the tier tables never scored, namely papillary renal cell carcinoma, diabetes mellitus and thrombotic disease.

The columns are arranged as the two runs, either side of the disease name, so that tier, composite score and the first fold-change column belong to the 13-indication run, whereas the second fold-change column, the rank and the call belong to the 1,000-indication run. The wording each run gives a row, together with the points to verify before that row is relied upon, is set out in the second table rather than compressed into the first.

Before those positions are read as a statement about biology, the way the narrower composite was assembled must be weighed alongside them: the input given the greatest weight in that score is prevalence of chromosomal instability, a quantity neither age-related row was assigned any value for, so part of the gap separating those two rows from the cancers above them follows from how the score was built rather than from anything measured in either class. The lowest band compounds that, since it names a category as well as a score range, so an age-related entry arrives in it partly on account of what it is. The evidence bearing directly on an aging indication is set out later on this page and does not depend on where these two rows landed.

A dash marks a value that was never printed rather than a result that missed a threshold, and every figure comes from the run named in the column note, at the precision that run prints it.

The first two columns are reproduced word for word and keep the spelling they were given, whereas the last column is written here and states how the rest of the evidence bears on the row beside it.

Ranking and verdict for the two age-related indications

Two age-related indications clear the filter applied in the wider run, neurodegenerative disease at rank 40 and diabetes mellitus at rank 37, and both are graded No-go on the ground that their scores arise from network co-embedding rather than from direct evidence, which is to say that they record the position KIF18A occupies within a protein interaction graph rather than the function KIF18A performs in an aged or diabetic tissue. The same conclusion is reached independently by querying aging directly, which returns an attention score of 0.000, and again from a third direction by the 13-indication run, which places neurodegenerative disease in its bottom tier, below every cancer it scored, while leaving diabetes mellitus outside its field altogether.

The finding is recorded within a Red reliability band, and the two age-related indications it concerns are ranked 40 and 37 out of the 1,000 indications that run scored; because the reason behind a grade carries further than the grade itself, the two sentences reproduced below are given in their recorded wording, setting out the basis on which those scores were reached.

A dash marks a field that was not recorded for that row, and the thrombotic indication is retained beside the other two so that the age-related verdicts are not read as the only negative calls the run returned.

Dimension scores returned by the direct aging query

Aging was queried directly rather than read off an indication list, and every dimension that would register a genuine disease association returned zero.

KIF18A is not one of the genes that change with age, given that the aging differential-expression meta-analysis returned 2362 genes at a false-discovery threshold of q below 0.05 and KIF18A was not among them. That absence is bounded by the instrument behind it, a meta-analysis pooled over aging expression datasets, and it does not govern the per-tissue correlations of expression against donor age reported later on this page, where a minority of the tissues tested reach significance at coefficients too small to account for much of the variation between donors. The meta-analysis is the reading carried forward here, because correlations of that magnitude do not establish an age-associated expression signal on their own.

Approached from the clinical trial record rather than from the omics data, the evidence returns the same answer, and it is recorded there without qualification.

The interactome community score and the pathway score measure the same network co-embedding named above, and they are the only above-baseline omics scores the aging query returned, both of them being attributable to KIF18A’s position in the mitotic network rather than to anything about aging. The three language-model dimensions beneath them are not omics measurements at all, in that they grade the tractability, the novelty and the on-target safety of the target itself rather than any association between that target and aging, so the highest score in the whole panel after the interactome measure is a statement about chemistry rather than evidence of an aging role.

Composite scores and the reproductive-aging contraindication

The 13-indication run sorted its two age-related entries, neurodegenerative disease at 3.5 and reproductive aging at 4.5, into a tier of their own against 9.2 for the leading cancer, and rejected the dual-purpose oncology-aging case for a KIF18A inhibitor outright.

The strongest aging link on record argues against inhibiting KIF18A rather than for it, since the reproductive-aging evidence is read as showing that KIF18A protects oocytes from aneuploidy, which makes inhibition the opposite of the intervention that evidence supports.

The one route left open is indirect and is itself graded speculative: aneuploidy drives cellular senescence, senescence is a hallmark of aging, and KIF18A dysfunction promotes aneuploidy in dividing cells. Every step of that chain runs through a cell that is actively dividing, and that requirement is the one the aging case has never been made to answer for.

The objection that presses hardest on the whole aging case is one of cell state rather than of evidence, in that KIF18A is taken to act only in mitosis while aged tissue is dominated by growth-arrested and post-mitotic cells that no longer divide and express very little of it. That premise is not uncontested, since a non-mitotic route has been described in which KIF18A drives epithelial-to-mesenchymal transition in hepatoma cells through an arachidonic acid pathway dependent on 5-lipoxygenase, and that route is named a non-mitotic oncogenic mechanism in as many words. The exception is narrower than the objection it qualifies, because a second activity demonstrated in dividing tumor cells establishes nothing about what the protein does inside a cell that has stopped dividing, and no measurement in arrested or post-mitotic tissue is offered on either side. The reading that supports the aging case does not deny the mismatch, and answers it by moving the target to cells that are still cycling and will later arrest, which is coherent and yet converts a treatment into prevention dosed over decades in healthy individuals. Settling that calls for a measurement in aged tissue rather than in a cell line, namely the fraction of the aneuploid burden still carried by cycling cells, together with a demonstration that an inhibitor lowers that burden in a living animal. The mismatch bears hardest on age-related neurodegeneration, where the target tissue is not a proliferating one, so that the No-go recorded against that indication follows from mechanism rather than from a measurement still to be made.

Statuses are reproduced in their recorded wording, and the second description of that rank is printed in the table of clock streams further down this page. There the KIF18A methylation site stands ninth of 227 features in the mammalian life-history clock, and that position is described at source as a top-ten feature whose coefficient direction is consistent with slower aging. The rank behind the two descriptions is identical and is not itself in dispute, and neither of them states the threshold at which a rank inside a field of a few hundred features becomes a leading one, so both are carried here rather than either being preferred.

Untapped indications in the wider run

The list holds one age-related indication among fourteen cancers, and the three scores that place it there are a protein interaction score, a matrix factorization score and a pathway score, whereas that same indication is graded No-go within the same run.

Names, areas and drivers are reproduced in their recorded wording, and near-duplicate rows are retained rather than merged, so that the ordering is read as it was returned rather than as a deduplicated version of it would appear. The names carry the capitalization of the wider run, which is not the capitalization the narrower run uses for the same diseases.

KIF18A was scored twice over fields of different size, and the two runs reported different quantities beneath a shared vocabulary of rank and score. The wider run scored a thousand indications across fourteen therapeutic areas on the PandaOmics prioritization engine and reported a position within that field, whereas the narrower run scored thirteen indications on a composite assembled for the assessment itself, graded out of ten and weighting the prevalence of chromosomal instability highest of its eight inputs, of which the wider run’s position is one. Two instruments therefore stand behind the orderings compared below, and at no point were the two sets of numbers reconciled with one another.

Where both runs name the same disease, both positions are carried below and neither is preferred, since there is no principled basis on which to prefer one. The chart draws every indication that the narrower run both placed in a tier and gave a position in the wider field, and the positions it prints beside bladder cancer, clear cell renal cell carcinoma and age-related oocyte aneuploidy are recorded by that run’s tier table alone, given that the wider run’s own tables place none of the three. The chart shows that the two orderings disagree: the indication ranked highest in the tier table sits twenty-second in the wider field, whereas the entry that same table places last sits fortieth.

A grade carries little information until the evidence beneath it has been named, and the thirteen indications graded in the 1,000-indication run, a set that overlaps the narrower run’s tiered thirteen without coinciding with it, are not supported to a comparable standard. Some rest on xenograft and patient-derived xenograft models together with active early-phase clinical programs, while others rest on cell-line expression and network inference alone, and the distinction matters more than the ordering the composite score produces.

The account below records the strength of the evidence behind each indication, the features that count in its favor and against it, and the databases from which each figure was drawn, together with the date on which each was accessed.

All thirteen grades come with a reason.

Every retrieval records the date it was made.

The mechanistic case is set out below as it has been constructed, together with the supporting literature adduced for it, and those citations stand as they were recorded rather than verified one by one against the papers they name.

The one failure the record does carry is a 2020 study filed under evidence for inhibition, although the compound it used is a kinesin potentiator that improves mitotic fidelity, and that contradiction is set out with the aging evidence rather than marked in this section.

The two lists hold nine mechanistic arguments and five recorded next steps, and they do not name the indications the same way, so that three of the headings appear word for word in the other list. They are set out below as each list recorded them rather than as pairs, because a pairing inferred from similar names risks filing a next step under an argument about a different indication.

Every sentence in the right-hand column is reproduced as it was recorded, citations included, and where one of those citations has been read against the paper it names, what the reading found is printed directly beneath the table.

Every one of these has a recorded result that would rule it out. Both columns are reproduced word for word, apart from two passages shortened where an ellipsis marks the words left out.

The table above is two entries shorter than its source promised: the evaluation undertook to record one next step for every Tier 3 candidate graded Go or Conditional, its own verdict table holds seven such candidates, and it wrote five. Prostate carcinoma and medulloblastoma, both graded Conditional at Tier 3, therefore carry no proposed next step and no result that would rule them out.

The aging argument advanced for KIF18A is a chain of four links: aging tissue accumulates aneuploid cells, those cells turn senescent, senescent cells inflame the tissue around them, and a drug that killed the proliferating aneuploid population selectively would therefore break the chain at its first link. Aneuploid cells that have already arrested or turned senescent sit outside the reach of a mitotic motor inhibitor, which confines the proposal to the dividing share of an aged tissue’s burden.

The links are cited unevenly: the passage from aneuploidy to senescence and from senescence to inflammatory signaling rests on published work, whereas the accumulation of aneuploid stem cells with age and the dispensability of KIF18A in healthy stem cells are advanced side by side with no supporting evidence for either. No experiment has yet carried the chain from its first link to its last, a gap acknowledged in four separate places by those who have argued for it.

Confidence was assigned on a five-point scale at source, and each grading is reproduced as it stands rather than recomputed from the claim and the limit printed beside it.

The four arguments were numbered in the order in which they were advanced at source, and that order is preserved here rather than being re-ranked by the weight of the evidence behind each.

Two kinds of measurement are offered as direct evidence that KIF18A is involved in human aging: the weight that aging clocks give it, whether of the epigenetic clock kind built on methylation marks or of the kind built on transcriptomic data, and how its expression changes with age across human tissues. The clock granting it the largest coefficient predicts the timing of sexual maturity across mammalian species rather than the age of any individual, a limit conceded in that row’s reading below.

Both are reproduced here exactly as they were derived, including at the points where the underlying numbers disagree with one another: the clock coefficients carry opposite signs on the same gene between two of the models, and a rise with age in some tissues is read alongside a fall in others as though the two observations supported a single conclusion.

Four discrepancies are reproduced here exactly as they stand rather than silently corrected in passing. KIF18A is stated three times to appear in 4 aging clocks, whereas the summary beneath carries the five rows listed here. The mammalian coefficient appears as +0.6686 in one place and rounded to +0.669 in another, which is one number at two precisions rather than two readings of it. The ZhangBLUP row names its feature as 11 CpG sites and tallies 8 negative against 4 positive, while the detail underneath it runs to 14 rows, 10 negative and 4 positive, which makes three incompatible counts of one set. PASTA and REG carry opposite signs on the identical gene identifier ENSG00000121621 from the same 2025 preprint, and both are counted in favor. One further overlap passes without comment: cg14927277 is both the AltumAge feature and row 13 of the ZhangBLUP table.

Each field is reproduced here as it stood on the date the resource was checked, rather than being re-queried for this page, so an entry added since would not appear.

Every lifespan figure in this table belongs to BubR1 or to p16-positive cell clearance, and none of it is a KIF18A measurement. The last row runs in the opposite pharmacological direction to inhibition, and the same study is elsewhere described as small-molecule inhibition. The mitotic-kinesin class to which KIF18A belongs supplies clinical precedent rather than longevity precedent. Ispinesib, an inhibitor of the related mitotic kinesin KIF11, was carried into Phase 2 in melanoma, head and neck squamous cell carcinoma, hepatocellular carcinoma, renal cell carcinoma and prostate cancer without an objective response in any of those trials, and the KIF18A inhibitor AMG 650 completed a Phase 1 study in advanced solid tumors. That class has never supplied a lifespan or healthspan measurement of any kind, since no healthy-volunteer study stands on record for any of these agents and no efficacy readout in aging has been reported anywhere in the class.

Were the aging case to be pursued, the shape such a program would have to take is itself the clearest available statement of how far the present evidence actually reaches, and it is set out below.

Every proposal listed begins with an experiment that has never been run, which is not a criticism of the proposals so much as a measurement of the gap they exist to close.

Four development positions are available, three of which command broad agreement: that the oncology program should run, that a standalone anti-aging program should not, and that an inhibitor should not be pointed at reproductive aging, where the evidence establishes that the target is protective. Agreement fails on the fourth, which is whether a single compound can be developed and described as both at once.

That split is left open in the assessments that follow immediately below, within this section, rather than resolved by assertion, because the measurement that would settle it has not been made in any species. Each position is therefore set out with the reasoning that supports it, and where two lines of reasoning lead to opposite conclusions from the same evidence, both are printed and the point of divergence is named.

Low-cost checks that require no new experiments

Four of the matters the evidence leaves open can be closed by consulting an existing record or by writing a sentence into a protocol, rather than by running an experiment. They are set out in the order in which they should be undertaken, with the least costly to settle standing first.

1. Read the ASCO abstract behind the clinical activity figure

   The figure rests on one abstract and one denominator, so every appearance of it stands or falls together rather than independently.

2. State the rank threshold the aging clock claim is applying

   The rank itself is printed on both sides of the disagreement, and only one of the two names the cut it is applying, so what divides the readings is where the line for a leading feature falls rather than the number sitting beneath it.

3. Name the object each of the program counts is enumerating

   A table of named assets that can be checked row by row already exists, and it settles the matter for that class of object.

4. Add senescence, SASP and aneuploidy readouts to the oncology protocols now, by amendment to the studies that are already enrolling

   Of the steps available, it is the only one that converts a trial already under way into evidence bearing on aging rather than on oncology alone.

Nothing argued above is stronger than the material it is drawn from, and that material has three distinct weaknesses. The case for a role in aging has never been tested directly; several of the figures attached to individual indications do not survive comparison with the tables beneath them; and the conclusion turns on evidence that does not yet exist.

Association rather than experiment as the basis of the aging case

The preceding parts assemble an argument out of correlated findings that no intervention has yet tested, and the distinction is worth stating in full before the individual weaknesses are set out. The accumulation of chromosomally abnormal cells in older tissue, the inflammatory phenotype those cells acquire once they turn senescent, and the selective dependence of such cells on this motor for survival have each been measured. Those measurements were made separately, however, in different systems and for different purposes, and what joins them here is inference rather than any single study that spans them.

Nothing has yet been dosed with an inhibitor of this motor and then followed to an endpoint that measures aging itself, which leaves the step from a coherent mechanism to a demonstrated effect untaken. The curated resources record the same silence, since the target carries a hallmark count of zero and no flag at all in the geroprotector, longevity-gene and trial-registry fields against which it was checked. Whether that silence records an absence of evidence or an absence of curation is itself unsettled, and the two readings are given equal standing here because the fields alone do not decide between them.

The ordering of indications on which much of this page depends inherits the same limit at one remove. A high position in that ordering records how prominently a target-disease pair figures across the scoring dimensions, which is a statement about the volume and recency of the literature behind a pair, the omics co-association measured for it and the funding attached to it. None of those quantities speaks to causation or to clinical validity, and the evidence underneath the ordering is thinner than a position in a ranked list makes it appear. The genetic association has not been fine-mapped, the expression values are taken pre-computed rather than recomputed, and the age-related entries in particular are recorded as having no direct mechanistic support of their own.

Figures printed against indications the underlying tables do not carry

Four of the ten entries registered below arise in the same way, and the mechanism behind them is better stated once than repeated underneath each of them in turn. In every case a differential-expression figure is printed in the scorecard against an indication for which the differential-expression table holds no row of any kind, so that a reader checking the cell against the table it summarizes finds nothing there to check it against.

Two things then happen, and which of them has happened decides how much weight the cell can bear. Sometimes the figure can be traced to a neighboring disease whose row does exist and whose value it reproduces to within the rounding, in which case the number is real and the label attached to it is not. Sometimes no table in either run prints the value against any disease at all, in which case the cell has no ancestor that can be found and is marked here as unsupported.

Nothing has been quietly repaired and no cell has been corrected in passing, which is a deliberate choice rather than an oversight. Each figure appears against the indication it was attached to, at the precision in which it was recorded, and the contents of the underlying table are set beside it. Both the printed value and the thing that stands behind it therefore remain visible at once, and the reader alone is left to decide what to make of the distance between them.

The verdict table farther up this page grades several of the indications whose cells are questioned in this register, and the effect of that questioning on the grades themselves is set down here. Non-small cell lung cancer carries a Go verdict resting on two grounds rather than one, and the trials named beside its expression claim survive untouched, so the loss of a figure belonging to another disease weakens that verdict without emptying it. Glioblastoma carries a Conditional verdict whose affirmative half rests on an omics signal the record never itemizes, and the only differential-expression figure it holds for that disease is the cell marked unsupported above, so the one quantity within that signal which can be checked does not survive. The position the disease holds in the wider ranking is untouched by this, as are the two mechanistic reports the record prints beside it, neither of which is an expression measurement. Prostate carcinoma carries a Conditional verdict resting on expression data, and neither expression table holds a prostate row at all, so that verdict also loses the ground its stated reason names. No call is rewritten in this register, because regrading an indication during transcription would substitute this page’s judgment for the one its source recorded.

Notes on how the remaining material has to be read

The other six entries are of a different order, in that several of them record disagreements between the underlying tables, yet none impeaches a figure this page itself relies on and none disturbs a conclusion drawn anywhere on it. Each of them nonetheless changes how a row beneath it should be understood by any reader who intends to carry that row somewhere else.

They concern a disease entered twice within one list under two names, two runs that place different kidney subtypes at the same position, a rank left blank in one table and filled in the other, a disease name spelled differently by the accounts that print it, and two readings of one measurement given on a single page and never reconciled. Each is reproduced as recorded rather than tidied, because a corrected spelling, a filled cell or a merged pair of rows would make the underlying material look more orderly than it is, and the orderliness so produced would belong to the transcription rather than to the record it is drawn from.

KIF18A is a kinesin-8 motor whose catalytic domain spans residues 11-355, and its tractability is settled by seven experimental structures, the sharpest 3LRE at 2.2 ångström. The therapeutic hypothesis this evidence carries is an oncology hypothesis resting on chromosomal-instability-selective synthetic lethality, cells with an unstable karyotype requiring the motor to complete division while stable cells tolerate its loss.

That selectivity is quantified as more than 40 percent toxicity in chromosomally unstable cells against less than 20 percent in stable and normal cells, although neither figure appears in the paper cited behind them. The furthest any program has gone is VLS-1488 in NCT05902988, where 7 of 17 evaluable patients showed tumor reduction, with no dose-limiting toxicity at any level in 52 patients treated at doses up to 800 mg.

The aging hypothesis rests on association rather than on intervention, its strongest quantitative support being an expression decline with age, steepest in ovary at r = -0.274 and p = 1.2 × 10⁻⁴ across 193 donors. The absent measurements are equally exact: the count of published lifespan or healthspan experiments using an inhibitor or a genetic model of the gene is 0, and the count entered against the gene in the Hallmarks of Aging targets database is recorded as 0.

Scored beside eleven cancers, both age-related indications fell into the lowest tier, the weakest cancer among them, clear cell renal cell carcinoma at 4.8, still outscoring age-related oocyte aneuploidy and reproductive aging at 4.5 and neurodegenerative disease at 3.5. The first of those two age-related indications has since been measured directly, and the result runs against the drug rather than behind it, motor-domain variants such as T273A prematurely raising oocyte aneuploidy in humans and in mice, the recorded human case being a homozygous carrier whose oocytes were 45 percent aneuploid. That finding settles the ovary alone, an inherited meiotic impairment being distinct from transient adult inhibition of somatic tissue.

The least costly of the aging measurements writes senescence, SASP and aneuploidy readouts into the oncology protocols by amendment, which alone converts a trial already recruiting into evidence about aging, a fall in senescent-cell burden moving the aging case from association to intervention and no movement leaving it where the composites place it. KIF18A is therefore a well-precedented oncology target with a quantified selectivity window and an early single-agent signal, and an unevidenced aging target whose strongest direct link to an aging tissue is an argument against inhibiting it there.

Target characterization drew on UniProt and NCBI Gene for sequence and domain architecture, on PDBe and the RCSB Protein Data Bank for experimentally determined structures, and on Ensembl Compara for paralog relationships and pairwise sequence identity, while human genetic evidence was taken from the GWAS Catalog and ClinVar and chemical and intellectual-property tractability from ChEMBL and FreePatentsOnline.

Disease association and indication ranking were produced with PandaOmics, which scored the target across the disease-indication space on 23 metrics in three families, those being curated disease omics datasets, biomedical literature volume with its recency and citation impact, and grant funding, each normalized between zero and one and combined into one composite rank across the full indication field. The four priority tiers printed on this page were not returned by that ranking but assigned by the narrower run, which banded a composite score of its own in which chromosomal-instability prevalence carried the heaviest weight and the ranking position entered as one input among several. Differential expression was derived from the PandaOmics expression meta-analysis, tissue-level and age-related expression from the Human Protein Atlas and GTEx, pathway and interaction membership from STRING v12.0 and Reactome, registered clinical activity from ClinicalTrials.gov through version 2 of its application programming interface, and supporting primary literature from PubMed.

Primary literature cited

Six published studies carry the core of the argument set out above, and they divide into three groups according to the role each one plays in it. The first establishes the synthetic-lethal vulnerability on which the oncology program is built, the middle four supply the chain that runs from chromosome missegregation through senescent-cell burden to lifespan, and the last is the only one of the six to test a small molecule against any link in that chain. Further primary work is cited by author and year at the point in the text where each result bears on the argument, whereas the identifiers for that wider literature stay in the record rather than being repeated at every mention, so this list records that core rather than the complete literature cited here.

1. Cohen-Sharir, Y. et al. (2021) Aneuploidy renders cancer cells vulnerable to mitotic checkpoint inhibition. NaturePMID 33505028
2. Baker, D. J. et al. (2004) BubR1 insufficiency causes early onset of aging-associated phenotypes and infertility in mice. Nature GeneticsPMID 15208629
3. Baker, D. J. et al. (2011) Clearance of p16Ink4a-positive senescent cells delays ageing-associated disorders. NaturePMID 22048312
4. Baker, D. J. et al. (2013) Increased expression of BubR1 protects against aneuploidy and cancer and extends healthy lifespan. Nature Cell BiologyPMID 23242215
5. Baker, D. J. et al. (2016) Naturally occurring p16(Ink4a)-positive cells shorten healthy lifespan. NaturePMID 26840489
6. Barroso-Vilares, M. et al. (2020) Small-molecule inhibition of aging-associated chromosomal instability delays cellular senescence. EMBO ReportsPMID 32134180

Glossary of terms

Aneuploidy

Having the wrong number of chromosomes in a cell. A healthy human cell carries forty-six; a cell that has gained or lost one is aneuploid. It accumulates with age and is close to universal in the tumors these programs target.

Chromosomal instability

A cell’s tendency to keep gaining and losing chromosomes each time it divides. It is the process; aneuploidy is the result. The trials described here choose patients by tumor type instead of by measuring it. Also written as: CIN, CIN-high, CIN-low

Kinesin

A family of motor proteins that walk along the internal fibers of a cell, carrying cargo or adjusting the fibers themselves. KIF18A is one of them, and the part that does the walking is called the motor domain.

Microtubule

The stiff hollow fibers a cell builds to pull its chromosomes apart when it divides. KIF18A walks along these and controls how fast their ends grow and shrink.

Synthetic lethality

When losing either of two things is survivable but losing both is not. Here it is the argument for the whole target: normal cells tolerate the loss of KIF18A, and cells whose chromosomes are already unstable do not.

Senescence

A state in which a damaged cell stops dividing but does not die, and instead persists in the tissue, releasing inflammatory signals. A senolytic is a drug that kills such cells. Also written as: senescent cells, senolytic

Senescence-associated secretory phenotype

The mixture of inflammatory proteins a senescent cell releases, which is how a single such cell degrades the tissue around it. Also written as: SASP

Epigenetic clock

A statistical model that estimates a person’s age from chemical marks on their DNA. The weight such a model assigns to KIF18A is frequently advanced as evidence that the gene participates in aging, an inference whose limits are examined in section 4.2.

Log2 fold change

The degree to which a gene is switched on in diseased tissue relative to healthy tissue, on a doubling scale. A value of one means twice as much; a negative value means less. Also written as: logFC

Geroscience endpoint

A measurement in a clinical trial that is about aging itself rather than about one disease, such as a biological-age estimate or a count of senescent cells. No KIF18A trial carries one.

Patient-derived xenograft

A piece of a patient’s tumor grown in a mouse, used to test whether a drug works against that particular tumor before trying it in people. Also written as: PDX

Companion diagnostic

A test used alongside a drug to decide who should receive it. For this target it would be a measurement of how unstable a tumor’s chromosomes are, and no threshold for it has been fixed.