Teclistamab (Tecvayli)

Teclistamab at a glance

Teclistamab is a T-cell-engaging immunotherapy given as an injection under the skin. Treatment starts with two small step-up doses before the first full dose. Current schedules differ for single-agent and combination treatment. Infection prevention and monitoring of protective antibodies remain important throughout.

This guide helps you prepare, manage everyday problems and recognise urgent symptoms. Your centre’s written dosing, observation and discharge plan remains essential.

What is teclistamab, and how does it work?

Teclistamab brings immune T cells close to target cells by recognising BCMA on plasma cells and CD3 on T cells. This helps the T cells attack the cancer cells. It is different from a checkpoint inhibitor, conventional chemotherapy or a medicine made from your own modified cells.

The immune activation that helps attack cancer can also release inflammatory signals. Treatment is therefore introduced and monitored carefully. Not every targeted antibody works this way, so instructions for another antibody medicine cannot be substituted.

How your team decides whether it is suitable

Teclistamab is used for selected adults with relapsed or refractory multiple myeloma. It may be prescribed alone after several previous treatments or with subcutaneous daratumumab in an eligible earlier treatment setting. The previous medicines and complete regimen determine eligibility and the dosing calendar.

The team reviews previous therapy, infection history, blood counts, kidney and liver tests and immunoglobulin levels. Let them know about repeated chest infections or previous severe reactions to immune therapies before the step-up course is booked.

Before treatment starts

Before starting, the team checks your blood counts, liver and kidney function and relevant infection tests. Screening may include hepatitis B and other viruses according to the drug and local protocol. Tell them about recent fever, cough, urinary symptoms, diarrhoea, dental infection or contact with an infectious illness. Treatment may need to wait until an active infection is controlled.

Explain any history of seizures, confusion, stroke, heart disease, low blood pressure or severe allergic reactions. Bring all prescriptions, non-prescription medicines and supplements. A person who knows you well can help describe your usual memory, speech and daily abilities, making later changes easier to recognise.

Discuss the practical plan before the first dose: transport, accommodation close to the centre where needed, a caregiver and access to urgent assessment. You need a working thermometer and clear instructions for contacting your own hospital’s urgent oncology service. Carry the treatment alert card and show it to other clinicians. Do not assume a general emergency department will know your exact dosing schedule without this information.

How treatment is given

The initial weight-based step-up doses are 0.06 mg/kg and 0.3 mg/kg, followed by a first treatment dose of 1.5 mg/kg. The exact spacing is prescribed, commonly with several days between doses. Single-agent treatment generally starts weekly, with less frequent dosing available to selected patients meeting response criteria. Current US information also includes a daratumumab-based combination with a different later dosing schedule; the single-agent calendar must not be copied onto that combination.

Current US instructions require hospitalisation for 48 hours after each of the two step-up doses. After the first full treatment dose, they require remaining near a healthcare facility and daily monitoring for 48 hours; individual patients may need admission. EU and local instructions can differ. A steroid, antihistamine and fever-reducing medicine are given before the specified early doses.

A gap in treatment may require repeating step-up dosing. Do not assume a previously tolerated full dose can be restarted immediately after illness or a long delay.

Practical care during the course

A healthcare professional gives the injection into the abdomen or thigh and rotates sites. The medicine comes in different strengths for preparation of step-up and treatment doses; staff check the correct vial and calculated amount. It is not a home self-injection.

Infection-prevention treatment can include medicines against Pneumocystis jirovecii pneumonia (PJP) and herpesvirus infection, and immunoglobulin replacement when indicated. Current US information explicitly calls for monitoring antibody levels and replacement to maintain adequate levels. Keep taking preventive medicines for as long as instructed, including during a treatment pause unless the team changes them.

Monitoring and checking whether treatment is working

Observation checks include temperature, pulse, blood pressure, breathing and oxygen levels. Staff also assess alertness, speech and coordination when appropriate. A simple writing task or orientation question is a safety check, not a test you are expected to practise passing.

Blood tests look for falling blood counts, liver problems, kidney changes and disturbances in salts or other chemicals. Depending on the medicine, protective antibody levels and infection-prevention needs are reviewed. New symptoms may lead to cultures, scans or other tests to separate infection from an immune reaction; both can occur together.

The team assesses benefit using the tests appropriate to your disease, which may include scans, blood measurements or bone-marrow assessment. A fever or rash does not prove treatment is working. Delays, repeat step-up dosing or stopping may be needed for safety. Tell the team about every interruption rather than assuming the next planned dose is still appropriate.

Common side effects and how to manage them

The pattern differs between medicines and accompanying treatments. The effects below are important practical possibilities, not a promise that everyone experiences them.

Tiredness and reduced stamina

Plan short periods of activity with rests and accept help during the early treatment phase. Gradually increase activity as your team advises. Sudden or profound tiredness, especially with dizziness, fever or breathlessness, needs assessment rather than being attributed automatically to treatment.

Fever, chills and aching

These can occur with immune activation, but can also indicate infection. Check your temperature and contact the oncology service using your emergency plan. Do not repeatedly take paracetamol to hide a fever. Staff may recommend it as a premedicine or for a reaction, but home fever needs the agreed assessment first.

Nausea, appetite change and bowel symptoms

Use prescribed anti-sickness medicine and try small meals and regular drinks, within any fluid restriction. Report persistent vomiting or diarrhoea. Inability to keep fluids or important medicines down needs urgent advice. Constipation can follow reduced activity or other medicines; request a suitable plan before it becomes severe.

Skin and administration-site reactions

Rash, itching or soreness at an injection or line site can occur. Use gentle washing, avoid rubbing and show the area to staff. Increasing heat, spreading redness, discharge or fever may suggest infection. Widespread hives, facial swelling, wheezing or collapse needs immediate help.

Blood-count changes

Some of these treatments can lower infection-fighting cells, red blood cells or platelets. This may cause infection, breathlessness, fatigue, bruising or bleeding. Keep scheduled blood tests, use a soft toothbrush and check before taking aspirin or anti-inflammatory painkillers. New unexplained bleeding, black stools or a severe headache needs urgent assessment.

Less common but important side effects

Cytokine release syndrome

T cells release messenger proteins called cytokines when activated. A large release can cause fever, shaking, fast heartbeat, low blood pressure and breathing problems. This is called cytokine release syndrome, or CRS. It can progress quickly and sometimes requires intensive care. Step-up doses and premedicines reduce risk but do not eliminate it.

CRS is often most relevant to early doses, but the timing varies and a later reaction remains possible. Do not diagnose an early fever as “just CRS”: infection can look similar and needs urgent investigation. Hospital treatment may include fluids, oxygen, medicines that block inflammatory signals and steroids, depending on the medicine and the reaction.

Neurological changes

Several T-cell-engaging treatments can cause brain or nervous-system effects, including immune effector cell-associated neurotoxicity syndrome, shortened to ICANS. It may occur with or separately from CRS. Warning signs include altered handwriting, trouble finding words, confusion, unusual sleepiness, tremor, poor balance or seizures. Risks are not identical for every engager, but a new neurological change always needs assessment.

A caregiver may notice a subtle change before you do. Do not let someone with confusion stay alone, drive or operate machinery. Severe confusion, inability to stay awake, a seizure or sudden weakness requires emergency care.

Serious infection

Immune activation against cancer does not mean normal infection protection is stronger. Cancer, previous treatment, low blood counts and reduced antibodies can all increase risk. Serious infections may occur during a dosing break or after treatment has ended. Take preventive medicines as prescribed and report respiratory, urinary, bowel or skin symptoms promptly.

Rapid cell breakdown and organ injury

With some treatments, rapid breakdown of cancer cells causes tumour lysis syndrome, changing blood chemicals and affecting the kidneys or heart. The team uses risk assessment, fluids and preventive medicines where needed. Reduced urine, persistent vomiting, muscle cramps, confusion or an irregular heartbeat needs urgent help. Liver inflammation or injury may first appear on a blood test; jaundice and dark urine should be reported.

Important points for this medicine

Low protective antibodies, low neutrophils and severe or opportunistic infections are major concerns. Fever may be absent in serious illness. The team also monitors liver injury and neurological toxicity. New confusion, walking difficulty or persistent headache can reflect more than one cause, including progressive multifocal leukoencephalopathy (PML), and should never be treated as an expected nuisance. The team withholds teclistamab while investigating suspected PML and stops it if confirmed.

If previous hepatitis B infection is identified, monitoring for reactivation continues during treatment and for at least six months afterwards. Report new local swelling or pain, especially back pain with weakness or altered bladder or bowel control; temporary tumour swelling can affect nearby nerves and needs urgent assessment.

Other medicines, supplements and vaccinations

Give the pharmacist a complete medicine list before starting and whenever something changes. Cytokine-related inflammation can temporarily change how the body processes some medicines, especially around early treatment or a reaction. Drugs with a narrow safe dose range may need additional checks. Do not adjust them yourself.

Take prescribed steroids, antihistamines, fever-reducing premedicines, infection prevention and tumour-lysis prevention on the specified days. Let the team know if a dose is missed or vomited. Avoid adding herbal or “immune-boosting” products without review; a product’s natural origin does not establish that it is safe with treatment.

Vaccines need planning with the team. Avoid live virus vaccines for at least four weeks before treatment, during treatment and for at least four weeks afterwards. Your team may advise a longer delay until immune recovery. Non-live vaccines may be appropriate, but the response can be reduced, particularly when B cells or protective antibodies are depleted. Household members can usually receive routine vaccines, with specific advice for any live vaccine or exposure concern.

Everyday life during treatment

The first treatment phase can require more support than later treatment. Arrange help with transport, meals, children or other dependants before admission or prolonged observation. A caregiver should know the warning symptoms and where you must be assessed. Keep your treatment record accessible rather than only in an app that may be unavailable in an emergency.

Eat regularly and follow the fluid plan given by the team. Drinking large amounts is not safe for everyone with heart or kidney problems. Maintain hand hygiene, safe food preparation and distance from people with active infections. Ask about work and public transport if blood counts or antibodies are low; your infection risk can change over time.

Build activity gradually and avoid tasks in which sudden dizziness or loss of concentration could harm you or others. Discuss travel before booking, because proximity and observation requirements may limit plans. Tell dentists and other clinicians about the treatment before procedures. Sex can be possible if comfortable, but pregnancy prevention remains necessary, and bleeding risk or illness may require temporary adjustments.

Driving and hazardous activities

Do not drive or use dangerous machinery during step-up dosing and for 48 hours after the step-up schedule has been completed, or whenever new neurological symptoms occur until they resolve. Follow any additional centre-specific restrictions and use a caregiver or arranged transport.

Fertility, contraception, pregnancy and breastfeeding

If you could become pregnant, use effective contraception during treatment and for five months after the last dose. Do not breastfeed during treatment and for at least five months afterwards. Account for daratumumab or any other accompanying medicine when agreeing the final precaution dates.

A pregnancy test may be needed before treatment. Contact the team promptly if pregnancy occurs or contraception fails. Effects on future fertility are not fully known; discuss preservation options before starting, especially if other treatment can affect fertility. The European patient leaflet also advises treated men whose partner could become pregnant to use effective contraception during treatment and for three months afterwards. Agree the partner precautions with your team. The complete regimen needs an individual plan.

After treatment finishes

The end of dosing is not necessarily the end of monitoring. Blood counts, protective antibodies and infection risk may take time to recover. Continue preventive medicines and any immunoglobulin replacement until the team tells you to change them. Keep the alert card and explain prior treatment when attending another hospital.

Follow the individual plan for scans, blood tests, vaccines and contraception. Report new neurological changes, repeated infections or persistent fatigue after treatment. Ask for a written summary of any serious reaction and the medicines used to treat it, because this information can affect later treatment decisions.

Frequently asked questions