This page shows what was measured, who it was measured in, and what that does not settle.
What Efalizumab does in the body
Formerly used as a weekly injection for severe plaque psoriasis.
White blood cells stick to the inside of blood vessels before they squeeze through the wall into tissue. That sticking uses a surface protein pair, and efalizumab is an antibody that covers one half of that pair. T cells then cannot grip the vessel wall properly, so far fewer of them reach the skin and the psoriasis plaques settle. The same grip is used by T cells that patrol the brain for a common dormant virus, and blocking it long enough allowed that virus to reactivate.
What happened in people
About one quarter of treated people had a major skin improvement, compared with one in twenty given a dummy treatment.
✓ Reviewed first-read answer
Where this came from
A person wrote this and a reviewer approved it against this exact record. It carries no effect size.
A reviewer approved this against this record. The reviewed-claim record carrying the exact population and effect size does not exist yet.
No source is stored against this line.
The limit that matters most
Four fatal brain infections were reported, but the risk per long-term user could not be calculated.
Where it acts
Circulating T lymphocytes and the dermal vascular endothelium; the toxicity site is central nervous system white matter
Kind of result
The kind of result is not recorded
Supervision
Professional supervision is normally required. A regulator classifies this substance in a way that restricts how it is supplied.
What the registries record it as
The substance registry classes this as protein.
FDA substance registry · XX2MN88N5D · read 2026-08-29
Where each sentence above came from
No recorded sentence describes the change this makes in a way that stands on its own. The page opens with what it is taken for instead, and the recorded explanation follows below.
Shown as the opening line on this page.
The limit a reviewer approved as the one that matters most here.
The four opening statements run to 118 words.
Words this page uses
Four words worth knowing first
Chosen from what this page shows, with each one explained before the word it depends on.
Stand-in result
A stand-in result is a number measured because the real result takes too long.
A picture of it, and where the picture fails
It is like judging a journey by the speedometer rather than by arriving.
Where that stops being true. Speed does predict arrival. Many stand-in results do not predict the real one.
What people get wrong. A stand-in result is often reported as the result itself.
A surrogate endpoint substituted for a clinical endpoint, valid only where the substitution has been shown to hold.
Enzyme
An enzyme is a protein that speeds up one chemical change.
A picture of it, and where the picture fails
An enzyme is like a machine on a production line doing one cut.
Where that stops being true. A machine is switched on and off by a person. Enzymes are controlled by the cell.
What people get wrong. Enzymes are thought to be used up. They are not; they work again and again.
A catalytic protein that lowers the activation energy of a specific reaction.
Receptor
A receptor is a part of a cell that a signal fits into.
A picture of it, and where the picture fails
A receptor is like a lock waiting for one key.
Where that stops being true. A lock either opens or does not. A receptor can be half-triggered, or worn out.
What people get wrong. Fitting a receptor is read as causing a benefit. It causes a step, and nothing more.
A protein that binds a specific ligand and converts that binding into a cellular response.
Pathway
A pathway is a chain of steps inside a cell, each one setting off the next.
A picture of it, and where the picture fails
A pathway is like a row of dominoes.
Where that stops being true. Dominoes fall one way. Pathways loop back and can switch themselves off.
What people get wrong. Changing one step is read as changing the outcome. Other steps often absorb it.
An ordered series of molecular interactions producing a defined cellular change.
What happened in people◇Read from sources, not yet reviewed
What was measured, goal by goal
One row for each goal a registered study measured something for. One column for each kind of thing that could be measured.
Registered studies list 5 outcome measures that RNAWiki could read. A registered study says what someone planned to measure. It does not say what they found. 0 of the matched studies tested this substance, and 0 posted a result.
There is no single score. A strong test result and a weak life result are different facts.
Goals down the side, kinds of measurement across the top. Each cell says what kind of thing was registered, not what was found.
Goal
Life outcome
What a body can do
How a person feels
A test result
A step in the body
Harms
How long
Who was studied
Blood sugar
∅Nothing in the sources checkedNo registered study lists a life outcome for this goal.
∅Nothing in the sources checkedNo registered study lists a performance measure for this goal.
∅Nothing in the sources checkedNo registered study lists a symptom measure for this goal.
△Only a number moved1 registered test measure.
∅Nothing in the sources checkedNo registered study lists a body-step measure for this goal.
—Not recordedHarms were not a registered measure for this goal.
—Not recordedNo finished study window is recorded.
…Waiting for a reviewerWho was studied is listed further down the page.
Which registered measures put each goal on this table
Blood sugar
insulin independent full islet graft function
Sorted by fixed word lists, version v1. A name the rules do not recognise stays unsorted rather than moving to the nearest column.
What each mark on this table means
∅ Nothing in the sources checked
No registered study lists a life outcome for this goal.
△ Only a number moved
1 registered test measure.
— Not recorded
Harms were not a registered measure for this goal.
… Waiting for a reviewer
Who was studied is listed further down the page.
What happened in people◇Read from sources, not yet reviewed
What happened in people
Each card is one study: the exact question it asked, who was in it, and whether it showed what it set out to show.
Improvement of 75 per cent or more in the Psoriasis Area and Severity Index at week 12
✓ The study showed what it set out to show
Who was studied
Phase 3 placebo-controlled trial of efalizumab in plaque psoriasis (Lebwohl et al.)
How many people
597
Study design
Phase 3
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
PASI-75 in 22 per cent at 1 mg/kg/week and 28 per cent at 2 mg/kg/week against 5 per cent on placebo, P < 0.001 for both
Repeated elsewhere
Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. The trial ran 12 weeks with 24 weeks of treatment in extension. Every PML case reported after approval occurred at three years or more of continuous exposure, a duration the registration programme could not have observed.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Subcutaneous injection, once weekly
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Confirmed PML cases by biologic agent approved for psoriasis, from approval to 30 January 2009
✓ The study showed what it set out to show
Who was studied
FDA Adverse Event Reporting System review of PML with psoriasis biologics
How many people
12
Study design
Post-marketing pharmacovigilance case series
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Efalizumab 4 cases, all in psoriasis, all fatal, all at three or more years of treatment; adalimumab 1, etanercept 3, infliximab 4, none in psoriasis and all confounded or unconfirmed
Repeated elsewhere
Partially Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. Spontaneous reporting has no denominator and is subject to underreporting, so a per-patient incidence rate was never established.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Subcutaneous injection, once weekly
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
RNAWiki holds 2 written-up human studies for this substance, each with the question it asked.
How we know it
Each card names the study, the number of people and what the study set out to measure.
What this does not prove
These summaries were written by a person and have not been signed off as reviewed claims.
Why it matters
A study that failed is as informative as one that worked, and both are here.
What we still do not know
No reviewed claim exists, so no exact population, effect size or interval is published yet.
What happened in people◇Read from sources, not yet reviewed
How close this is to real life
The top step is something a person would feel or care about. The bottom is a guess from software. Filled steps are where evidence exists for this substance.
■Living longer, or avoiding a major eventEvidence recorded. Death, a heart attack, a stroke, a hospital stay.1 registered measure of this kind. No reviewed result.
□What a body can do day to dayNo evidence recorded. Walking, dressing, breathing, recovering.No registered study measures this.
□Measured performanceNo evidence recorded. How much was lifted, how far was run, how fast.No registered study measures this.
□Symptoms and quality of lifeNo evidence recorded. Pain, tiredness, mood, sleep, as the person rated it.No registered study measures this.
■A number that stands in for healthEvidence recorded. Cholesterol, blood sugar, bone density. A stand-in, not the thing itself.1 registered measure of this kind.
■A step measured inside a personEvidence recorded. Something measured in human tissue or human cells.A human record sits on the stored organism ladder.
■AnimalsEvidence recorded. Mice, rats, dogs. Useful for ideas, not proof about people.Stored records in Mouse, Rat. A result in animals says what to test next. It does not say what happens in people.
□Cells in a dishNo evidence recorded. Cells or chemistry on a bench, far from a whole body.No cell or bench record is stored.
□A guess from softwareNo evidence recorded. Nobody measured it. RNAWiki never publishes one as a finding.RNAWiki stores no prediction for this record. Software can suggest a link. RNAWiki does not publish one as a finding.
Higher on these steps means closer to something a person would feel. It does not mean better done.
What it changes in the body◇Read from sources, not yet reviewed
The path through the body
From what a person takes to what changes. A solid line is a step measured in people. A dashed line is a step nobody has measured that way.
Start
Efalizumab
What a person takes: Subcutaneous injection, once weekly.
The measurement behind this step
Weekly subcutaneous humanised IgG1 antibody with a conditioning first dose. Target-mediated clearance means exposure rises non-linearly once CD11a occupancy saturates, and surface CD11a downmodulation means immune function recovers more slowly than drug concentrations fall.
Getting in
A weekly injection under the skin
Given once a week as a subcutaneous injection, often self-administered.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Subcutaneous efalizumab, a conditioning dose followed by weekly maintenance dosing at 1 mg/kg. Clearance is target-mediated and saturable, so steady-state exposure rises disproportionately once CD11a is fully occupied.
In the bloodstream it coats a specific protein on the surface of T cells and pulls some of it off the surface entirely.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Binds the alpha-L subunit of LFA-1 on circulating lymphocytes, producing both steric blockade and downmodulation of surface CD11a, which is why lymphocyte counts rise and functional recovery lags the drug's clearance.
Without that protein working, T cells cannot hold on to the inside of blood vessels long enough to squeeze through into tissue.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
LFA-1 can no longer engage ICAM-1 on activated endothelium, so firm adhesion and transendothelial migration fail. The same blockade impairs the LFA-1/ICAM-1 immunological synapse required for T-cell activation by antigen-presenting cells.
Fewer T cells reach the plaque — and fewer reach the brain
Far fewer T cells enter the skin, so the psoriasis inflammatory loop breaks. The same block applies to the T cells that keep a dormant brain virus in check.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Reduced T-cell trafficking into dermis and epidermis interrupts the IL-23/Th17 keratinocyte loop. The same reduction in transendothelial migration applies at the blood-brain barrier, permitting reactivation of JC polyomavirus in oligodendrocytes.
Plaques clear in a quarter of patients; four developed fatal PML
About a quarter of patients had a major improvement in their skin. Four patients developed a fatal brain infection after three or more years of treatment.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
Measured: PASI-75 in 22 to 28 per cent at 12 weeks against 5 per cent on placebo. Measured: four confirmed PML cases in psoriasis patients in the FDA adverse event database, all fatal, all after three or more years of treatment.
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 5 steps from taking it to an effect in a person.
How we know it
Each step names the study behind it in the technical detail beside it.
What this does not prove
A change inside the body is a reason to look. It is not a result in a person.
Why it matters
A reader can see exactly where the chain stops being measured in people.
What we still do not know
No reviewed claim binds any of these steps to a named population.
What it would be like to take◇Read from sources, not yet reviewed
Felt, measured, or meaningful
Three different things that get called the same word. Registered studies measured all three, and mixing them is how a blood test becomes a health claim.
Felt
Things a person could notice without a test.
No registered study measured anything of this kind.
Measured
Things only a test, a scale or a device shows.
insulin independent full islet graft function
Meaningful
Things that change how a life goes, not only a number.
renal allograft survival
A registered study says what someone planned to measure. It does not say what they found. A number moving is not the same as a life going better. The two are shown apart here.
Felt, but not shown to help. A person notices a change. No study showed it leads anywhere good.
Measured, but not felt. A number moves. The person notices nothing. Both can be true.
Measured, but not shown to matter. A number moves in the good direction. Nobody showed that lives went better.
Matters, but takes years. The result that counts may take longer than anyone would keep watching.
Names that fit none of the three (3)
pasi psoriasis area and severity index
experiencing adverse events
psoriasis area and severity index
These are harms, study-process measures, or names the rules did not recognise. They are shown rather than dropped.
What is missing or unclear◇Read from sources, not yet reviewed
Were people like you studied?
RNAWiki cannot tell whether a study fits you. It can show who was in it, and where the result stops carrying.
Who was studied
People similar to this profile were included.
Nobody. The product is withdrawn worldwide. Patients on it in 2009 were transitioned to other systemic agents, which by then included the TNF inhibitors and ustekinumab.
Who is missing from the studies
Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
Where the result stopped carrying
Marketing authorisation suspended in the European Union in February 2009 and voluntarily withdrawn in the United States the same year
The registration programme observed 12 to 24 weeks; the harm appeared at three years and later
Discontinuation itself carried rebound and severe flare risk, so the withdrawal required managed transition rather than a stop order
This is a scope explorer, not a diagnosis engine.
It shows who was studied so you can see whether people similar to you were included.
RNAWiki cannot tell whether a study fits you. It can show who was in it.
What it would be like to take◇Read from sources, not yet reviewed
Why it might seem to do nothing
A real effect and a noticed effect are different things. These are the recorded reasons the two come apart.
It was studied for a different goal
The studies measured something else entirely.
On this record: Some registered studies measured things that match no goal on this page.
It was studied in different people
The people in the studies were not much like the reader.
On this record: Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
The change is too small to feel
A real change can still sit below what a person notices.
On this record: Natalizumab, blocking the same functional step through a different integrin, returned under a monitoring programme; efalizumab did not
The evidence may simply be wrong
Small early studies often do not hold up.
On this record: RNAWiki has not yet published a reviewed conclusion for this use.
Other reasons RNAWiki checked and found nothing for (9)
A different form was studied
The studied form is not the form on the shelf. Nothing in this record points to this reason.
There was nothing to correct
Where a level is already normal, topping it up may change nothing. Nothing in this record points to this reason.
Something else had to happen too
In the studies it was paired with training, a diet or another treatment. Nothing in this record points to this reason.
Day-to-day swing hides it
Sleep, food, stress and time of day move most numbers more than this would. Nothing in this record points to this reason.
Not enough time yet
The studies ran longer than the person has waited. Nothing in this record points to this reason.
It was not taken as studied
Missed days change the result, and studies count them. Nothing in this record points to this reason.
Something else changed at the same time
Two changes at once cannot be told apart afterwards. Nothing in this record points to this reason.
The product may not be what it says
Contents of a sold product are not always what the label states. Nothing in this record points to this reason.
No recorded reason
RNAWiki has nothing stored that would explain it. Nothing in this record points to this reason.
None of these is a reason to take more. Taking more is not a step this page ever suggests.
What it would be like to take◇Read from sources, not yet reviewed
What taking it involves
The recorded facts about getting hold of it and using it. Nothing here is a suggestion about what you should do.
How it is supplied
Withdrawn
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Read from the recorded approval status.
No source is stored against this line.
Form and route
Subcutaneous injection, once weekly
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form and route recorded on this substance.
No source is stored against this line.
Who oversees it
Professional supervision is normally required. A regulator classifies this substance in a way that restricts how it is supplied.
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Suppression classes recorded: S1, S8.
No source is stored against this line.
What is in the pack
Weekly subcutaneous humanised IgG1 antibody with a conditioning first dose. Target-mediated clearance means exposure rises non-linearly once CD11a occupancy saturates, and surface CD11a downmodulation means immune function recovers more slowly than drug concentrations fall.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on how this is sold and what that means for what is in the pack.
No source is stored against this line.
Where it is registered
Regulatory records are listed in the technical disclosure at the foot of this page.
# Counted from records
Where this came from
A count of rows RNAWiki holds. It describes our records, not your body.
Register entries are stored per jurisdiction and shown with their dates.
No source is stored against this line.
Why people stop
Not recorded.
∅ Nothing recorded
Where this came from
RNAWiki holds nothing here and says so rather than guessing.
No record of why people stopped taking it is stored for this substance.
No source is stored against this line.
What it would be like to take◇Read from sources, not yet reviewed
What can go wrong
Sorted by where each line came from. A regulator's label and a report somebody sent in are not the same kind of fact.
·Worth asking a clinician aboutWritten into the record from the studies named on this page
Withdrawn worldwide in 2009. The decisive harm was progressive multifocal leukoencephalopathy: four confirmed cases in psoriasis patients in the FDA adverse event database, all fatal, all after three or more years of continuous treatment. Other recognised effects were first-dose flu-like reactions, thrombocytopenia, haemolytic anaemia, immune-mediated arthritis, and rebound or severe flare of psoriasis on discontinuation, including erythrodermic and pustular presentations.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
These are reports people sent to a regulator. They do not show the medicine caused the reaction.
Nobody counted how many people took the medicine and reported nothing.
The same event can be reported more than once, and many reports are incomplete.
News coverage, lawsuits and new warnings change how often people report.
A count is not a rate and not a risk.
Efalizumab appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 558 reaction mentions were counted. One report can name several reactions.
The recorded terms (10)
psoriasis — 264 reaction mentions
white blood cell count increased — 60 reaction mentions
myalgia — 47 reaction mentions
psoriatic arthropathy — 36 reaction mentions
influenza like illness — 34 reaction mentions
arthritis — 33 reaction mentions
skin exfoliation — 28 reaction mentions
lymphocyte count increased — 21 reaction mentions
lymphocytosis — 18 reaction mentions
dermatitis exfoliative — 17 reaction mentions
open-targets-adr · recorded 2026-06-24 · a recorded source, not a stored snapshot
Over a long time. No completed tested study window is recorded, so long-term effects are not established by the registry record.
Groups the studies covered thinly. Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What is missing or unclear∅Nothing found in the sources checked
Does the exact form matter?
Evidence belongs to the exact thing that was tested. A different salt, a different mixture or a different preparation is a different question.
The form that was studied
Subcutaneous injection, once weekly
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form used in the studies cited on this page.
No source is stored against this line.
What is sold
Target-mediated clearance means exposure rises non-linearly once CD11a occupancy saturates, and surface CD11a downmodulation means immune function recovers more slowly than drug concentrations fall.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on which forms are sold and how they compare.
No source is stored against this line.
Evidence carries across two names for one substance. It does not carry across a salt, a mirror form or a mixture.
What it would be like to take◇Read from sources, not yet reviewed
What you could measure
This one is decided with a clinician, so this section holds questions to ask rather than a plan to run.
Self-experiment planning is not offered for a prescription or clinician-supervised medicine, withdrawn medicine. The questions below are for a clinician or pharmacist.
Questions worth asking
Which of the trials of Efalizumab studied people like me?
What was measured, and for how long?
Was the result a laboratory value or a health outcome?
What would we watch for, and when would we stop?
Tracking can show whether something changed for you. It cannot show what caused it.
RNAWiki records evidence. It does not say whether this substance is right for you.
What is missing or unclear◇Read from sources, not yet reviewed
Claims that go past the evidence
Things said about this substance that sound reasonable, and the exact step that is missing between the evidence and the claim.
✗Goes past the evidence
That a per-patient PML incidence rate is known — the analysis has a numerator of four and no denominator of long-duration exposures
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That a safe treatment duration exists below three years; the authors state explicitly that none has been defined
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That the PML cases reported with anti-TNF agents in the same review are comparable — those occurred in other conditions with confounding immunosuppression
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
What is missing or unclear◇Read from sources, not yet reviewed
What nobody knows yet
Open questions, each with why it is open and what would close it.
How much did people take in the studies?
The sources RNAWiki checked hold nothing for this field.
Why it matters. A result belongs to an amount. Without the amount the result floats free.
What would answer it
A stored source that records it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
How fast does the body clear it?
The sources RNAWiki checked hold nothing for this field.
Why it matters. Without this, nothing on this page can say how long anything lasts.
What would answer it
A stored source that records it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing populations
Which groups were under-represented in the studies has not been recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing long-term data
No completed tested study window is recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
No reviewed conclusion
RNAWiki has not yet published a reviewed conclusion for this use.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing interaction studies
No interaction was found in the registers checked. Not finding one is not the same as showing there is none.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Formulation uncertainty
Several salts, forms or products of Efalizumab are recorded. Results from one form may not transfer to another.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Mechanism not reviewed
No reviewed mechanism story exists for this substance.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
What happened in people◇Read from sources, not yet reviewed
Check any of this yourself
Every line above traced back to the study it came from. This is the technical layer, and the vocabulary changes here.
Every line above can be traced to the study named beside it. Follow the link and read it.
PASI-75 in 22 to 28 per cent at 12 weeks against 5 per cent on placebo
In plain words
In the pivotal trial of 597 patients, about a quarter of those on efalizumab had their psoriasis score fall by three quarters at 12 weeks, against one in twenty on placebo.
What was measured
PASI-75 response rate at 12 weeks, efalizumab versus placebo
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Phase 3 multicentre randomised placebo-controlled double-blind trial in 597 subjects with moderate to severe plaque psoriasis, randomised to subcutaneous efalizumab 1 mg/kg/week, 2 mg/kg/week, or placebo for 12 weeks. At week 12, an improvement of 75 per cent or more in the Psoriasis Area and Severity Index occurred in 22 per cent at 1 mg/kg and 28 per cent at 2 mg/kg, against 5 per cent on placebo (P < 0.001 for both). Separation from placebo was evident by week 4 (P < 0.001). Among efalizumab-treated responders at week 12, response was maintained through week 24 in 77 per cent of those who continued against 20 per cent of those switched to placebo. After discontinuation at week 24, PASI-50 was maintained in roughly 30 per cent over the following 12 weeks.
Written into the record, not signed off as a reviewed claim
Four PML cases in psoriasis patients, all fatal, all after three or more years
In plain words
The FDA searched its adverse-event database for brain infections reported with every psoriasis biologic. Efalizumab was the only one with cases in psoriasis patients. All of them died.
What was measured
Confirmed PML cases by psoriasis biologic in the FDA Adverse Event Reporting System through 30 January 2009
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
FDA Office of Surveillance and Epidemiology searched the Adverse Event Reporting System for post-marketing reports of progressive multifocal leukoencephalopathy associated with the biologics approved for psoriasis — adalimumab, alefacept, efalizumab, etanercept and infliximab — from approval to 30 January 2009. Twelve cases suggestive of PML were identified: adalimumab 1, efalizumab 4, etanercept 3, infliximab 4. Efalizumab was the only drug with cases occurring in the setting of psoriasis. All four efalizumab cases presented three years or more after treatment initiation, and all resulted in death. The cases attributed to the other agents occurred in conditions other than psoriasis and were confounded by concurrent immunosuppression or were not confirmed PML.
Written into the record, not signed off as a reviewed claim
The mechanism was demonstrated directly in a treated patient
In plain words
In one patient, researchers measured how well T cells could cross a vessel wall while on the drug, and again after it was removed. Migration recovered as the blocked protein reappeared.
What was measured
T-cell transendothelial migration against LFA-1 surface expression, before and after plasma exchange
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Two patients with severe psoriasis treated for three years or more developed fatal PML with JC virus identified in cerebrospinal fluid; both died two and six months after onset despite plasma exchange and signs of immune reconstitution, with PML confirmed neuropathologically. Serial studies in one patient showed that efalizumab treatment was associated with reduced transendothelial migration by peripheral T cells in vitro, and that as LFA-1 expression on peripheral T cells rose after plasma exchange, in vitro migration increased with it. That is a direct dose-response measurement of the proposed mechanism in the affected patient rather than an inference from the drug's target.
Written into the record, not signed off as a reviewed claim
The same mechanism, the opposite regulatory outcome, in the same years
In plain words
Natalizumab blocks a closely related adhesion protein, also caused PML, and was brought back under a monitoring programme. Efalizumab was not. The difference is what the alternatives looked like.
What was measured
Not recorded
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Natalizumab, an anti-alpha-4-integrin antibody, was withdrawn in February 2005 after three PML cases and returned in June 2006 under a restricted distribution and monitoring programme. Efalizumab, an anti-CD11a antibody blocking the same functional step in a different integrin, was withdrawn in 2009 and never returned. The distinguishing facts are not mechanistic. Natalizumab reduced the relapse rate by 68 per cent in relapsing multiple sclerosis, a progressive neurological disease with limited alternatives. Efalizumab produced PASI-75 in a quarter of psoriasis patients at a time when ustekinumab was being approved and the TNF inhibitors were established. When the benefit is modest and substitutes exist, a monitoring programme does not change the arithmetic.
Written into the record, not signed off as a reviewed claim
No incidence rate was ever established, only a numerator
In plain words
Four cases were reported. Nobody knows how many people had taken the drug for three or more years, so the actual risk per patient was never calculated.
What was measured
That a per-patient PML incidence rate for efalizumab is known
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The FDA analysis rests on spontaneous post-marketing reports, which the authors identify as limited by underreporting and by variable quality of information. There is a numerator — four confirmed cases in psoriasis — and no reliable denominator of patients treated for three or more years, which is the exposure window in which every case occurred. Statements of the form "the PML risk with efalizumab was one in N" therefore do not derive from the evidence base that caused the withdrawal. The authors were explicit that a treatment duration which does not place patients at risk has not been defined. The decision was made on four fatal cases with a plausible and later demonstrated mechanism, not on a rate.
Written into the record, not signed off as a reviewed claim
Withdrawal came from Europe first
In plain words
The European Medicines Agency recommended suspension in February 2009. The United States withdrawal followed in the same year.
What was measured
Not recorded
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
The European Medicines Agency's Committee for Medicinal Products for Human Use recommended suspension of the Raptiva marketing authorisation on 19 February 2009, concluding that the benefits no longer outweighed the risks given the reports of PML. Genentech announced a phased voluntary withdrawal from the United States market, completed in 2009. The sequence matters for reading the record: the European suspension is a formal regulatory act with a published assessment, while the United States exit was a sponsor decision, so the two jurisdictions leave different kinds of document behind for the same event.
Source
European Medicines Agency, Raptiva (efalizumab): withdrawn medicine, marketing authorisation withdrawn 2009; Kothary N et al. J Am Acad Dermatol 2011;65:546-551
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
verified
Review state
Written into the record, not signed off as a reviewed claim
Rebound psoriasis on withdrawal was a documented problem of stopping it
In plain words
Stopping the drug abruptly could make psoriasis flare worse than before, which complicated moving thousands of patients off it at once.
What was measured
Maintenance of PASI-75 on continued treatment versus switch to placebo, and PASI-50 maintenance after discontinuation
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The pivotal trial measured what happens on discontinuation: among subjects who achieved PASI-75 at week 12 and were then switched to placebo, response was maintained in 20 per cent against 77 per cent of those who continued, and after treatment stopped at week 24 only about 30 per cent maintained even PASI-50 over 12 weeks of follow-up. Rebound and severe flares including erythrodermic and pustular presentations were recognised on discontinuation. The 2009 withdrawal therefore required a supervised transition rather than a stop order, which is a class of harm that a withdrawal itself creates and that a withdrawal notice does not usually count.
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What is not here
5 questions this page could not answer
These sections were prepared and left out because there was nothing to put in them. They are listed rather than hidden, so the gaps in this record are visible.
How long anything takes — found nothing in the sources checked.
What it may clash with — found nothing in the sources checked.
Other ways to the same goal — found nothing in the sources checked.
How this medicine reached us — found nothing in the sources checked.
What changed on this page — found nothing in the sources checked.
The record as stored
The full record, for auditing
Everything above is built from what is below. This layer keeps the technical vocabulary, record identifiers and every stored row, so a reader who wants to check the page can.
The older medicine-wide conclusion held in this record
Written for a clinical reader, and about the medicine as a whole rather than about one indication, population and set of trials. RNAWiki does not treat it as a programme conclusion and no reviewer has signed it off in that form. It is here word for word because it is what the record holds.
A humanised anti-CD11a antibody that produced PASI-75 in 22 to 28 per cent of patients against 5 per cent on placebo at 12 weeks, withdrawn in 2009 after four reports of progressive multifocal leukoencephalopathy in psoriasis patients — every one of them fatal, and every one after three or more years of continuous treatment.
Recorded evidence blocks (7)
Q2
What did Efalizumab's largest trial (1200 people) and its longest (9 years) measure?
1200 people in Efalizumab's largest registered study, 9 years in its longest registered window, measuring Mean concentrations of anti-<phi>X174 antibodies in the FU period 2 weeks after the FU Day 70 vaccinations in Group A compared with mean antibody concentrations 2 weeks after the Treatment Day 63… ClinicalTrials.gov · 2026-09-01
11 phase2, 10 phase1, 8 phase3, 7 phase4, 2 na, 1 na or unstated; NCT00276250; 2014-12; no ageing endpoint recorded. Last human test completed 2014, NCT00276250.
Interpretation These counts include studies where Efalizumab was a comparison treatment, a background treatment or an exposure in an observational study, and the longest window may be a planned end date. Trial roles have not yet been classified for this record.
Show the evidence
phase2
11
phase1
10
phase3
8
phase4
7
na
2
na or unstated
1
1 more recorded row
Last recorded human testNCT00276250
2014-12
recorded 2026-09-01 · last checked 2026-09-04
Q3
From mouse to human: where has Efalizumab shown lifespan?
Mean concentrations of anti-<phi>X174 antibodies in the FU period 2 weeks after the FU Day 70 vaccinations in Group A compared with mean antibody… — the recorded outcome words.
Show the evidence
mouse
mechanism-only
rat
lifespan
humanNCT00382512
biomarker; Mean concentrations of anti-<phi>X174 antibodies in the FU period 2 weeks after the FU Day 70 vaccinations in Group A compared with mean antibody concentrations 2 weeks after the Treatment Day 63 vaccination in Group C; 34
recorded 2026-09-01 · last checked 2026-09-04
Q4
11 of Efalizumab's trials stopped: safety, accrual/recruitment, other?
terminated; "Raptiva was withdrawn from the market"
5 further recorded trials
NCT00676559
withdrawn; "Unrelated serious adverse events involving one of the proposed medications"
NCT00737763
withdrawn; "drug withdrawn from market"
NCT00746980
withdrawn; "Newly identified safety concerns have changed the risk and benefit considerations"
NCT00777400
withdrawn; "New safety information reported in the post-marketing setting with efalizumab for treatment of chronic plaque psoriasis and trial conduct feasibility issues."
NCT00972543
terminated; "The study was terminated after the European Medicines Evaluation Agency recommended to suspend the marketing authorisation of Raptiva in the European Union"
recorded 2026-09-01 · last checked 2026-09-04
Q5
Which of experiencing adverse events, insulin independent full islet graft function and pasi psoriasis area and severity index did Efalizumab's trials measure?
experiencing adverse events, insulin independent full islet graft function and pasi psoriasis area and severity index lead 5 outcome terms across Efalizumab's trials. ClinicalTrials.gov · 2026-09-01
Interpretation renal allograft survival and psoriasis area and severity index follow.
Show the evidence
pasi psoriasis area and severity index
1
experiencing adverse events
1
insulin independent full islet graft function
1
renal allograft survival
1
psoriasis area and severity index
1
recorded 2026-09-01 · last checked 2026-09-04
Q6
Which 14 trials of Efalizumab posted no result?
Posted no result
14 of 14 completed trials
Registrations
NCT00109317, NCT00109252, NCT00034203, NCT00051662, NCT00096980 and NCT00338143, and 8 more
Completion dates
oldest 2003-02; newest 2007-07
Show the evidence
Trial
NCT00109317
2003-02
NCT00109252
2003-04
NCT00034203
2003-08
NCT00051662
2004-02
NCT00096980
2004-05
NCT00338143
2004-05
8 further recorded trials
NCT00096603
2004-07
NCT00256139
2004-10
NCT00133107
2005-11
NCT00442650
2005-12
NCT00226057
2006-05
NCT00134134
2006-08
NCT00312026
2006-11-28
NCT00302445
2007-07
Q7
At the median, Efalizumab's trials enrolled 11 people — anything larger?
Median enrolment
11
Largest enrolment
1200
Registered trials counted
32
Q8
What do 558 spontaneous reports say about Efalizumab — and not say?
These are reports people sent to a regulator. They do not show the medicine caused the reaction. Nobody counted how many people took the medicine and reported nothing. The same event can be reported more than once, and many reports are incomplete. News coverage, lawsuits and new warnings change how often people report. A count is not a rate and not a risk.
Efalizumab appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 558 reaction mentions were counted: psoriasis 264; white blood cell count increased 60; myalgia 47; psoriatic arthropathy 36. open-targets-adr · CHEMBL1201575 · 2026-06-24
Show the evidence
psoriasis
264
white blood cell count increased
60
myalgia
47
psoriatic arthropathy
36
influenza like illness
34
arthritis
33
4 more recorded rows
skin exfoliation
28
lymphocyte count increased
21
lymphocytosis
18
dermatitis exfoliative
17
recorded 2026-06-24 · last checked 2026-09-04
Where it is registeredIdentifiers, relations and other names
ChEMBL ATC CC BY-SA · ClinicalTrials.gov — US Government work · Europe PMC — metadata only, under the recorded legal gate · Open Targets 26.06 — CC0 · derived from this page's own recorded fields; no external licence · mixed register set; per-register licences in docs/specs/corpus-20k-sources.md
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