The FDA has a sensible approach about monoclonal antibodies. There is a recognition that if you can get to a plasma level of antibodies which in a lab will neutralise currently circulatIng COVID-19 virus variants then you are likely to be protected. As the vitus mutates then some antibodies lose their effect altogether. Others retain their effect but may require a higher dose to do so. This applies to Evusheld.

The U.S. Food and Drug Administration has revised the emergency use authorization for Evusheld (tixagevimab co-packaged with cilgavimab) to change the initial dose for the authorized use as pre-exposure prophylaxis (prevention) of COVID-19 in certain adults and pediatric patients.

Based on the most recent information and data available, Evusheld may be less active against certain Omicron subvariants. The dosing regimen was revised because available data indicate that a higher dose of Evusheld may be more likely to prevent infection by the COVID-19 Omicron subvariants BA.1 and BA.1.1 than the originally authorized Evusheld dose.

Previously, the authorized Evusheld dosage was 150 mg of tixagevimab and 150 mg of cilgavimab administered as two separate consecutive intramuscular injections, with repeat doses every six months while SARS-CoV-2 remains in circulation. With this EUA revision, FDA has increased the initial authorized dose to 300 mg of tixagevimab and 300 mg of cilgavimab. Patients who have already received the previously authorized dose (150 mg of tixagevimab and 150 mg of cilgavimab) should receive an additional dose of 150 mg of tixagevimab and 150 mg of cilgavimab as soon as possible to raise their monoclonal antibody levels to those expected for patients receiving the higher dose.

https://www.fda.gov/drugs/drug-safety-and-availability/fda-authorizes-revisions-evusheld-dosing?fbclid=IwAR3g4fyS1CkO5VqT9ObixoJEHC6kXcAmJ0uWX1l1lptMrBrWj-bvc8yrCb8

Given the constraints in supply of this life saving treatment it is bad news to hear the urgent announcement from the FDA that the dose of Evusheld needs to be doubled,

What this means is if you have had a dose then you are likely NOT protected at the moment and should urgently talk to your doctor about having a second dose to boost to the level needed.

If you are due to have Evusheld you will need to have double the dose that has been given so far.

If you are relying on Evusheld then you are also likely to need repeat doses sooner than was planned. It is also possible that Sotrovimab, the only antibody currently approved for covid treatment may also need a higher dose in the future.

What does this mean for the rest of us? It seems likely that wherever your spike antibodies have come from you need s higher level in your blood to continue to be protected. If your body responds to vaccines then booster shots will increase these levels and may well be life saving. If you have a few antibodies from IVIG or SCIG then the level is not likely to be high enough.

Also one other implication of this news is that as the virus mutates it is also possible that older monoclonal antibodies we have shelved due to resistance might start to work again. Clearly we may need a cocktail of several monoclonal antibodies in the future and ongoing development of new ones is crucial.

We should think of antibodies as our first line of defence. Fortunately if we get sick despite having them, antivirals are a valuable second line. Other treatments can also be used if we get more sick and need hospital.

Remember also that whilst a fear of covid is reasonable, the majority of blood cancer patients who get an infection will not get severe disease.

Read the announcement from the FDA

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