Elonva (Corifollitropin Alfa)

What Is Elonva and What Is It Used For?

Elonva contains the active substance corifollitropin alfa, a modified recombinant follicle-stimulating hormone (FSH) that belongs to the group of medicines known as gonadotropins. Gonadotropins play a critical role in human fertility and reproduction. FSH, one of the key gonadotropins, is essential for the growth and maturation of ovarian follicles—the small fluid-filled sacs in the ovaries that contain eggs. In males, FSH is necessary for the initiation and maintenance of spermatogenesis (sperm production) and testicular development.

What makes Elonva unique is its extended duration of action. Unlike conventional recombinant FSH preparations that require daily injections, Elonva provides sustained follicle-stimulating activity for approximately seven days from a single subcutaneous injection. This is achieved through a chimeric protein design: the alpha-subunit of human FSH is combined with the carboxy-terminal peptide of the human chorionic gonadotropin (hCG) beta-subunit. This structural modification significantly extends the molecule's half-life, allowing for once-per-cycle dosing during the initial phase of ovarian stimulation.

Use in Women (IVF and Assisted Reproduction)

Elonva is indicated for controlled ovarian stimulation (COS) in women undergoing assisted reproductive technologies (ART) such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). During these procedures, the goal is to stimulate the ovaries to produce multiple mature follicles simultaneously, rather than the single follicle that develops during a natural menstrual cycle. This maximises the number of eggs available for retrieval, fertilization in the laboratory, and subsequent embryo transfer to the uterus.

In a standard IVF protocol, Elonva is given as a single injection on the first day of ovarian stimulation. It replaces the first seven days of daily recombinant FSH (recFSH) injections. After day 7, if additional stimulation is needed, the treating physician may continue with daily recFSH injections until a sufficient number of follicles have reached appropriate size, as determined by ultrasound monitoring. A GnRH antagonist is typically started on day 5 or 6 after the Elonva injection to prevent premature ovulation. When follicular maturation is adequate, a trigger injection of human chorionic gonadotropin (hCG) is administered, and egg retrieval is performed 34–36 hours later.

Use in Adolescent Males (Delayed Puberty)

Elonva is also approved for use in adolescent males aged 14 years and older who have delayed puberty caused by hypogonadotropic hypogonadism (HH). This is a condition in which the pituitary gland or hypothalamus does not produce sufficient gonadotropin-releasing hormones, resulting in inadequate stimulation of the testes. Without treatment, affected young men fail to develop normal secondary sexual characteristics and may have impaired testicular function.

In this population, Elonva is administered once every two weeks by subcutaneous injection, in combination with human chorionic gonadotropin (hCG). The initial 12 weeks of treatment involve Elonva alone (given every two weeks), after which hCG is added. The combined treatment with hCG (administered twice weekly at doses of 500–5,000 IU) may continue for 52 weeks or longer to achieve full pubertal development. The dose of Elonva is determined by body weight: 100 micrograms for young men weighing 60 kg or less, and 150 micrograms for those over 60 kg.

What Should You Know Before Taking Elonva?

Contraindications

Do not use Elonva if you have any of the following conditions. These are absolute contraindications that make treatment with this medicine unsafe or inappropriate:

• Allergy to corifollitropin alfa or any of the other ingredients in the medicine (sodium citrate, sucrose, polysorbate 20, methionine, water for injections)
• Cancer of the ovaries, breast, uterus, or brain (pituitary gland or hypothalamus)
• Unexplained vaginal bleeding that is not menstrual and where the cause has not been determined
• Primary ovarian insufficiency—ovaries that do not function due to an inherent condition
• Ovarian cysts or enlarged ovaries not caused by polycystic ovary syndrome
• Reproductive organ malformations that make normal pregnancy impossible
• Uterine fibroids (myomas) that would prevent a normal pregnancy

Warnings and Precautions

Ovarian Hyperstimulation Syndrome (OHSS)

Treatment with gonadotropins such as Elonva carries a risk of ovarian hyperstimulation syndrome (OHSS). This is a serious medical condition caused by excessive ovarian response to stimulation. The growing follicles become larger than normal, and in severe cases, the ovaries can enlarge dramatically. Fluid may accumulate in the abdominal and chest cavities, potentially leading to dangerous complications including blood clots (thromboembolism), kidney failure, and in rare cases, OHSS can be life-threatening.

Your doctor will perform regular ultrasound examinations of the ovaries and may check blood hormone levels to monitor the response to treatment carefully. It is critical that you attend all scheduled monitoring appointments. Contact your doctor immediately if you experience severe abdominal swelling and pain, nausea, vomiting, sudden weight gain due to fluid retention, diarrhoea, reduced urine output, or difficulty breathing.

Elonva must only be administered once during a single treatment cycle. Giving a second dose significantly increases the risk of developing OHSS. After the initial seven days of Elonva activity, any additional ovarian stimulation should be performed with standard daily FSH preparations under close medical supervision.

Ovarian Torsion

Ovarian torsion is a condition in which an ovary twists on its supporting ligaments, potentially cutting off its blood supply. This is a recognised complication of ovarian stimulation, particularly when the ovaries become enlarged. Inform your doctor if you have any history of ovarian torsion, previous abdominal surgery, or ovarian cysts, as these factors may increase your risk.

Blood Clots (Thromboembolism)

Treatment with gonadotropins, like pregnancy itself, can increase the risk of blood clot formation (thrombosis). Blood clots can cause serious medical conditions including pulmonary embolism (blockage in the lungs), stroke, heart attack, deep vein thrombosis (DVT), and thrombophlebitis. Discuss your individual risk with your doctor before starting treatment, particularly if you have a personal or family history of thrombosis, known clotting disorders, or if you are significantly overweight.

Multiple Pregnancies

There is an increased risk of twin or higher-order multiple pregnancies with fertility treatment, even when only a single embryo is transferred to the uterus. Multiple pregnancies carry increased health risks for both the mother and her babies, including preterm delivery, pre-eclampsia, and low birth weight. Your fertility specialist will discuss strategies to minimise this risk, such as single embryo transfer (SET) when appropriate.

Ectopic Pregnancy

If Elonva treatment results in pregnancy, there is an increased risk of ectopic pregnancy (a pregnancy that develops outside the uterus, typically in a fallopian tube). Your doctor will perform an early ultrasound examination to confirm that the pregnancy is in the correct location within the uterus.

Pregnancy and Breastfeeding

Do not use Elonva if you are already pregnant or think you may be pregnant, or if you are breastfeeding. Elonva is intended to achieve pregnancy through assisted reproduction—once pregnancy is confirmed, treatment with Elonva and other gonadotropins must be stopped. Always inform your healthcare provider if there is any possibility of pregnancy before receiving treatment.

Other Medical Conditions

Before starting Elonva, inform your doctor if you have any of the following conditions, as they may affect treatment decisions or require additional monitoring:

• Kidney disease
• Uncontrolled pituitary or hypothalamic disorders
• Underactive thyroid (hypothyroidism)
• Adrenal insufficiency
• High prolactin levels (hyperprolactinaemia)
• Diabetes, heart disease, or other chronic conditions
• Any condition where pregnancy would be medically dangerous

Driving and Operating Machinery

Elonva may cause dizziness in some patients. If you experience dizziness, do not drive or operate machinery until the symptom resolves.

How Does Elonva Interact with Other Drugs?

Clinical experience with Elonva has not revealed significant pharmacokinetic or pharmacodynamic drug interactions. However, because Elonva is part of a carefully orchestrated fertility treatment protocol, the timing and sequencing of concurrent medications is critical. Your fertility specialist will manage the precise timing of all medications in your treatment cycle.

Medications Used Alongside Elonva

During controlled ovarian stimulation for IVF, Elonva is typically used in combination with the following medications as part of a structured treatment protocol:

Protocols Not Recommended

The use of Elonva in combination with a GnRH agonist protocol (also called a “long protocol”) is not recommended. Clinical data for Elonva are primarily based on GnRH antagonist protocols, which are the standard of care when using this medication. Using Elonva with a GnRH agonist may alter the ovarian response in unpredictable ways and has not been adequately studied for safety and efficacy.

Effect on Pregnancy Tests

An important consideration during Elonva treatment is the potential for false-positive pregnancy tests. Because of the structural similarity between corifollitropin alfa and hCG (both share the CTP element), standard pregnancy tests may show a false-positive result during or shortly after treatment. Your doctor will advise you on when it is appropriate to perform a pregnancy test and how to interpret the results correctly. If you get a positive pregnancy test, always consult your fertility specialist before drawing conclusions.

What Is the Correct Dosage of Elonva?

Elonva dosing is individualised and must always be prescribed and supervised by a physician experienced in treating fertility problems or endocrine disorders. The dose is determined by body weight and, in women, also by age. Self-injection may be performed at home after proper instruction from a healthcare professional, but the first injection should ideally be administered under medical supervision.

Dosage for Women (IVF / Controlled Ovarian Stimulation)

A single injection is given on day 1 of ovarian stimulation. During the first seven days after the injection, no additional recombinant FSH should be administered. From day 8 (seven days after the Elonva injection), your doctor may decide to continue stimulation with a standard daily FSH preparation. This additional stimulation may continue for several days until a sufficient number of follicles have reached appropriate size, as confirmed by ultrasound monitoring. The FSH treatment is then stopped and final oocyte maturation is triggered with an hCG injection. Egg retrieval is performed 34–36 hours later.

Dosage for Adolescent Males (Delayed Puberty / HH)

Concurrent hCG treatment (500–5,000 IU twice weekly) may be necessary for 52 weeks or longer to achieve full adult sexual development. Elonva should be administered on the same day of the week each time, in the morning.

How to Inject Elonva

Elonva is administered as a subcutaneous injection (under the skin), preferably just below the navel. The injection should be given into a skin fold pinched between the thumb and index finger. The pre-filled syringe is equipped with an automatic safety system that retracts the needle after use, helping to prevent needlestick injuries. Follow these general steps:

1. Wash your hands thoroughly with soap and water and dry them.
2. Clean the injection site with an antiseptic (such as alcohol) and allow it to dry for at least one minute.
3. Prepare the syringe by holding it with the grey cap pointing upward and gently tapping it to move air bubbles to the top.
4. Unscrew the cap, attach the needle, and remove the needle guard.
5. Gently push the plunger until a small drop appears at the needle tip.
6. Pinch a fold of skin, insert the needle at a 90-degree angle, and slowly push the plunger down until it stops.
7. Hold the plunger in place and count to five to ensure the full dose is delivered.
8. Release the plunger—the needle retracts automatically and locks in place.

Do not inject Elonva into a muscle. The injection must always be given subcutaneously.

Missed Dose

If you forget to inject Elonva on the scheduled day, contact your doctor immediately. Do not inject Elonva without first speaking with your doctor. Timing is critical in fertility treatment and delayed puberty protocols, and your doctor will advise whether the cycle can continue or needs adjustment.

Overdose

If you suspect you have used too much Elonva, or if additional recombinant FSH has been given too early or in excessive amounts, contact your doctor or nearest emergency department immediately. Overdose may increase the risk of ovarian hyperstimulation syndrome (OHSS), which can be serious. Symptoms of overdose may include severe abdominal pain, nausea, vomiting, and rapid weight gain.

What Are the Side Effects of Elonva?

Like all medicines, Elonva can cause side effects, although not everybody gets them. The most clinically significant risk is ovarian hyperstimulation syndrome (OHSS), which can range from mild discomfort to a life-threatening emergency. The frequency and severity of side effects vary between women undergoing IVF treatment and adolescent males being treated for delayed puberty.

Side Effects in Women

Side Effects in Adolescent Males

Serious Side Effects Requiring Immediate Attention

The first symptoms of ovarian hyperstimulation may present as abdominal pain, nausea, or diarrhoea. OHSS can develop into a serious medical condition with enlarged ovaries, fluid accumulation in the abdomen and chest (which may cause sudden weight gain), and blood clots. Even if symptoms appear several days after the injection, contact your doctor promptly.

Ectopic pregnancy (pregnancy outside the uterus) and multiple pregnancies have also been reported in association with assisted reproductive technology but are not considered directly related to Elonva itself. In rare cases, treatment with gonadotropins including Elonva has been associated with thromboembolic events, where blood clots form in blood vessels and may travel to block blood flow in the lungs, brain, or other organs.

How Should You Store Elonva?

Proper storage of Elonva is essential to maintain the medication's stability and effectiveness. The pre-filled syringe must be handled and stored according to specific conditions to ensure the corifollitropin alfa solution remains safe for injection.

Pharmacy Storage

At the pharmacy, Elonva is stored in a refrigerator at 2–8°C. The medication must not be frozen, as freezing can damage the protein structure of the active substance and render it ineffective or potentially harmful.

Patient Storage at Home

You have two options for storing Elonva at home:

1. Refrigerated storage: Keep in the refrigerator at 2–8°C. Do not freeze.
2. Room temperature storage: Store at or below 25°C for a maximum of one month. Note the date you first remove the syringe from the refrigerator and use it within one month from that date.

Always keep the syringe in the outer carton to protect it from light. Light exposure can degrade the active substance over time.

When Not to Use Elonva

• Do not use after the expiry date printed on the label (after “EXP”) and the carton. The expiry date refers to the last day of that month.
• Do not use if the syringe has been stored outside the refrigerator for more than one month.
• Do not use if it has been stored above 25°C at any point outside the refrigerator.
• Do not use if the solution is not clear and colourless.
• Do not use if the syringe or needle appears damaged or broken.

Dispose of used or unused syringes according to local regulations. Do not throw them in household waste or down the drain. Ask your pharmacist how to properly dispose of medicines that are no longer needed. These measures help protect the environment.

Keep this medicine out of the sight and reach of children at all times.

What Does Elonva Contain?

Active Substance

The active substance in Elonva is corifollitropin alfa, a recombinant fusion protein produced by Chinese hamster ovary (CHO) cells through recombinant DNA technology. Each pre-filled syringe contains either 100 micrograms or 150 micrograms of corifollitropin alfa dissolved in 0.5 millilitres (mL) of solution.

Inactive Ingredients (Excipients)

The other ingredients in Elonva are:

• Sodium citrate – buffering agent to maintain pH stability
• Sucrose – stabiliser to protect the protein during storage
• Polysorbate 20 – surfactant to prevent protein aggregation
• Methionine – antioxidant to protect the active substance
• Water for injections – solvent

The pH may have been adjusted with sodium hydroxide and/or hydrochloric acid. This medicine contains less than 1 mmol sodium (23 mg) per injection, meaning it is essentially sodium-free.

Appearance and Packaging

Elonva is a clear, colourless aqueous solution for injection supplied in a pre-filled syringe with an automatic safety system to prevent needlestick injuries after use. The syringe is packaged together with a sterile injection needle. Each syringe contains 0.5 mL of solution. The pre-filled syringe comes in packs of one syringe.

Elonva is available in two strengths: 100 micrograms and 150 micrograms solution for injection. The marketing authorisation holder and manufacturer is N.V. Organon, based in Oss, the Netherlands.

References

1. European Medicines Agency (EMA). Elonva Summary of Product Characteristics. Last updated 2023. Available at: EMA – Elonva EPAR.
2. Devroey P, Boostanfar R, Koper NP, et al. A double-blind, non-inferiority RCT comparing corifollitropin alfa and recombinant FSH during the first 7 days of ovarian stimulation using a GnRH antagonist protocol. Human Reproduction. 2009;24(12):3063–3072. doi:10.1093/humrep/dep291
3. Boostanfar R, Mannaerts BMJL, Witjes H, et al. A randomized controlled trial comparing a corifollitropin alfa-based versus a daily rFSH-based protocol in women undergoing controlled ovarian stimulation. Fertility and Sterility. 2012;98(6):1479–1485.
4. European Society of Human Reproduction and Embryology (ESHRE). Guidelines on Ovarian Stimulation for IVF/ICSI. 2024.
5. World Health Organization. WHO Model List of Essential Medicines. 23rd list, 2023.
6. Fares FA, Suganuma N, Nishimori K, et al. Design of a long-acting follitropin agonist by fusing the C-terminal sequence of the chorionic gonadotropin beta subunit to the follitropin beta subunit. Proceedings of the National Academy of Sciences. 1992;89(10):4304–4308.
7. British National Formulary (BNF). Corifollitropin alfa. Available at: bnf.nice.org.uk.

Editorial Team