The Andexxa Showpiece

Every so often a masterclass performance arises in the medical literature. A performance transcending the boundaries of what was once thought possible. A shining exemplar of human achievement.

This is a trial, published in the New England Journal of Medicine, with the following features:

• Conducted by an institute sponsored by pharma.
• Designed by the first author, a consultant for pharma, and two employees of pharma.
• Written by a medical writer employed by pharma.
• Replete with authors reporting multiple financial conflicts of interest with pharma.
• Substantially modified trial procedures and outcomes two and three years into the trial.
• Introduced an interim stopping rule whose analysis was performed by an unblinded statistician affiliated with the funded institute.
• Stopped the trial early based on the new interim stopping rule.
• Used a surrogate composite primary endpoint.
• Allowed the “usual care” arm to include patients who did not receive an active treatment comparator.
• Permitted discrepancies in the baseline characteristics favoring the experimental arm.

And, this is solely the reported mechanisms by which pharma has placed their hands on the scales of this trial. It ought to be quite clear these procedures were carefully designed to ensure the (financial) success of this trial, and its ultimate publication is virtually an advertorial for the product in question.

The culprit this go-around? AstraZeneca née Alexion née Portola for Andexxa – better known as “andexanet alfa” (even though the FDA declined their drug naming for this label, properly known as “Coagulation Factor Xa [Recombinant], Inactivated-zhzo”). The trial is ANNEXA-I, which purports to be a comparison between Andexxa and Prothrombin Concentrate Complexes.

As alluded to above, this trial was not designed to permit Andexxa to fail. With Andexxa sales climbing and approaching $200M annually, it is obviously impermissible to allow a trial to offer a hint of doubt – especially considering Portola/Alexion/AstraZeneca have been investing in “expert guidelines” aimed at elevating Andexxa above PCCs as first-line treatment for Factor Xa-associated bleeding.

So – naturally, Andexxa “succeeds”. On the composite endpoint of “good hemostatic efficacy” – hematoma volume change < 35%, NIHSS change < 7 points, and no use of rescue therapy between 3-12 hours – Andexxa outperformed “usual care” by 13.4%, 67.0% to 53.1%. The primary limiting factor to this composite endpoint was the sub-endpoint of hematoma volume change of < 35%. And, as this composite favours Andexxa, the trial was stopped early – and the favorable press releases roll in. Ideally, this is the point at which our sponsors would like us to stop further analysis and critique.

Interestingly, the main paper presents an efficacy analysis consisting of 452 patients. However, between the initiation of the interim analysis and cessation of trial procedures, the authors enrolled an additional 78 patients. The authors report findings from all 530 in their safety analysis, but exclude them from the primary efficacy analysis – consigning the full cohort analysis to a supplementary appendix. There is no obvious reason to do so – other than the fact the larger cohort demonstrates less favorable results for Andexxa, with the hemostatic efficacy composite dropping from 67.0% to 63.9%. As is frequently cautioned regarding stopping trials early, doing so inflates the confidence intervals, diminishes the precision of an effect size estimate, and precludes the natural propensity of regression to the mean.

Then, there are the trial procedures. Prior to a protocol amendment excluding subdural hematomas, the Andexxa group included 13 patients with SDH, as compared with only 4 in “usual care”. Subdural hematomas, generally speaking, have far less sinister an outcome than intracerebral hemorrhage – an imbalance favoring the Andexxa cohort. Then, bizarrely, only 85% of the “usual care” cohort received anticoagulation reversal using PCCs. Very little data is included regarding these 60 patients receiving “non-PCC” care at the discretion of their treating clinicians. What sort of selection bias led clinicians to withhold an active treatment for ICH? Without concrete data, it is impossible to do more than speculate, but it seems logical to theorize these patients must have been disadvantaged by their lack of treatment.

Next, there are The Downsides. Treatment with Andexxa very clearly causes increased arterial thrombotic events. Ischemic strokes occurred in 6.5% of those treated with Andexxa, as compared to 1.5% receiving “usual care”. Myocardial infarctions occurred in 4.2% of those treated with Andexxa, as compared to 1.5% of those receiving “usual care”. A smaller excess of pulmonary embolism was seen in the “usual care” arm, however.

Lastly, there are the patient-oriented outcomes. Naturally, with a trial stopped early due to a composite surrogate, the authors are quick to mention the trial is underpowered to evaluate these endpoints. However, the overall outcomes of patients included in this trial are grim – and they are more grim for those treated with Andexxa. At 30 days, only 28% of patients treated with Andexxa achieved a modified Rankin scale of 0 to 3, compared with 31% in the “usual care” cohort. Similarly, 27.8% of patients treated with Andexxa had died at 30 days, as compared with 25.5% of those receiving “usual care”.

So, there you have it – such a “success” story of a trial it needed to be stopped early, and we still have no clear evidence Andexxa ought to be favored over “usual care”. The authors merrily cite INTERACT1, the trial upon which the “hematoma growth” surrogate is “validated” – and they will rely on this heavily for marketing purposes. In the end, we have exactly what we ought to have expected from a trial designed to stand on its head to deliver for its product, and we as clinicians are ever-poorer for it.

Andexanet for Factor Xa Inhibitor-Associated Acute Intracerebral Hemorrhage