Subcutaneous Infliximab (Zymfentra) for Crohn's Disease

For many of us living with moderate-to-severe Crohn's disease, biologic therapy has been life-changing - but the reality of regular infusion-center visits can be exhausting. Subcutaneous infliximab for Crohn's disease now offers a different path. In October 2023, the FDA approved Zymfentra (infliximab-dyyb), making it the first and only self-injectable form of infliximab available in the United States (3)(6). This approval opens a genuinely new option: the same proven anti-TNF molecule, delivered at home with a simple injection every two weeks.

Key Takeaways

• In the LIBERTY-CD phase 3 trial, 62.3% of patients on subcutaneous infliximab achieved clinical remission at week 54 versus 32.1% on placebo (1)(3)
• Endoscopic response at week 54 was 51.1% with subcutaneous infliximab versus 17.9% with placebo (1)(3)
• Two-year extension data published in 2025 showed 63.5% sustained clinical remission with no new safety signals (2)
• The standard maintenance dose is 120 mg injected every two weeks, after completing IV induction at weeks 0, 2, and 6 (1)(6)
• Subcutaneous dosing may produce more stable trough drug levels and potentially lower rates of anti-drug antibodies compared to IV infusion
• Zymfentra carries the same boxed warnings as all infliximab products, including risks of serious infections and malignancy

What Is Subcutaneous Infliximab (Zymfentra)?

Subcutaneous infliximab (Zymfentra) is a self-injectable formulation of the anti-TNF biologic infliximab, approved for maintenance therapy in adults with moderately to severely active Crohn's disease. It delivers the same active molecule used in IV infliximab but through a simple injection under the skin rather than a lengthy infusion appointment (3)(6).

Infliximab has been a cornerstone of Crohn's treatment for over two decades. As we covered in our overview of anti-TNF therapies in Crohn's disease, this class of biologics works by blocking tumor necrosis factor-alpha, a key driver of gut inflammation. Zymfentra (infliximab-dyyb, also known as CT-P13 SC, made by Celltrion) is a biosimilar-based subcutaneous formulation that was approved by the FDA on October 23, 2023 (3)(6).

How Zymfentra Differs From IV Infliximab (Remicade)

The core difference is delivery. IV infliximab requires visits to an infusion center every 6 to 8 weeks, with each session lasting roughly two hours plus monitoring time. Zymfentra, by contrast, is a prefilled syringe or autoinjector pen that you use at home in a matter of minutes. The drug itself targets the same inflammatory pathway - what changes is how it reaches your bloodstream.

It is worth noting that Zymfentra was already approved earlier in Europe as Remsima SC, where it has been building real-world evidence in IBD patients. That European experience has provided reassuring data about what patients and clinicians can expect in practice (5).

Why a Subcutaneous Anti-TNF Matters for Crohn's

For a disease that already demands so much of your time and energy, removing the need for regular infusion visits is meaningful. Beyond convenience, the subcutaneous route offers pharmacokinetic differences that may matter clinically - more on that below. For patients who respond well to infliximab but find the infusion schedule burdensome, this represents a genuine shift in how treatment fits into daily life. As we explored in our article on biologic treatments past and present, this kind of delivery innovation is part of a broader trend toward making effective therapies more accessible and patient-friendly.

How Self-Injection Works: Dosing and Practicalities

The treatment follows a two-phase approach. Patients first complete standard IV infliximab induction at weeks 0, 2, and 6, then transition to subcutaneous maintenance with 120 mg injected every two weeks (1)(6). This means you still need those initial infusion appointments, but after that, routine infusion-center visits are no longer necessary.

Induction Then Maintenance: The Two-Phase Schedule

The IV induction phase is important because it rapidly builds up therapeutic drug levels in your system. Once you have completed those three induction infusions and your gastroenterologist confirms you have responded, you begin the subcutaneous maintenance injections. The 120 mg dose every two weeks was the regimen validated in the pivotal LIBERTY-CD trial.

What a Typical Injection Day Looks Like

The practical side is straightforward. You remove the prefilled syringe or autoinjector from the refrigerator and let it warm to room temperature. Injection sites include the thigh or abdomen, and it is recommended to rotate between sites to reduce irritation. The injection itself takes only seconds. Many patients describe it as comparable to other subcutaneous biologics they may have used. Storage does require refrigeration, so planning around travel is worth thinking through in advance.

What the LIBERTY-CD Trial Showed

The LIBERTY-CD trial was a phase 3, randomized, double-blind, placebo-controlled study that tested subcutaneous CT-P13 as maintenance therapy after IV induction in Crohn's disease. The results provided the clinical evidence behind the FDA approval and remain the most important dataset for understanding what this treatment can deliver (1)(3).

Week 54 Outcomes

At week 54, clinical remission was achieved by 62.3% of patients receiving subcutaneous infliximab compared with 32.1% on placebo (P less than .0001) (1)(3). Endoscopic response - a measure of actual mucosal healing visible on colonoscopy - was 51.1% versus 17.9% (P less than .0001) (1)(3). These are meaningful differences, and the endoscopic response numbers are especially encouraging because mucosal healing is increasingly recognized as a key treatment goal.

A post hoc analysis of the LIBERTY-CD data found that the benefit held regardless of where Crohn's disease was located in the gut. Clinical remission rates were 60.95% in patients with ileum-dominant disease and 66.95% in those with colon-dominant disease, both significantly higher than placebo (4). This is reassuring for patients whose disease primarily affects one region.

Two-Year Extension Data

Results from the open-label extension of LIBERTY, published in 2025, showed that 63.5% of Crohn's patients maintained clinical remission at two years (2). Importantly, no new safety signals emerged over this longer follow-up period. These extension data suggest that the efficacy seen at week 54 is durable and that subcutaneous infliximab continues to work well for patients who respond to it initially.

Who Is It For? (and Who It's Not For)

Zymfentra is approved for adults with moderately to severely active Crohn's disease who have already responded to IV infliximab induction (6). In practice, this means it is most relevant for patients who are doing well on infliximab and want to move away from regular infusion visits, or for patients newly starting infliximab who prefer a home-based maintenance option.

It may also be considered for patients who are losing response on standard IV dosing. Extension trial data have explored dose escalation to 240 mg in some patients, though this remains an area of active research. However, Zymfentra is not appropriate as a first-ever dose without prior IV induction - you need those initial infusion appointments. It is also not used during active uncontrolled infections.

Patients who previously developed significant immunogenicity (anti-drug antibodies) on IV infliximab need careful review by their gastroenterologist before considering any switch. The decision to transition should always be individualized, weighing your specific disease history, current response, and practical needs.

Pharmacokinetic and Practical Advantages

One of the less-discussed but clinically meaningful benefits of subcutaneous dosing is its pharmacokinetic profile. Compared to IV infliximab given every 6 to 8 weeks, the every-two-week subcutaneous regimen produces more stable, consistently higher trough drug levels. This matters because low trough levels have been linked to loss of response and higher rates of anti-drug antibody formation.

Studies suggest that subcutaneous dosing may be associated with lower rates of neutralizing anti-drug antibodies compared to IV dosing in some patient populations. As we discussed in our therapeutic drug monitoring guide, tracking trough levels can help your gastroenterologist optimize your treatment - and the steadier levels from subcutaneous dosing may simplify that process.

From a practical standpoint, the advantages extend beyond pharmacokinetics. Fewer infusion visits mean less missed work, less travel, and no need for IV access. An Australian real-world study of 40 IBD patients (27 with Crohn's) who switched from IV to subcutaneous infliximab found that 82% remained in clinical remission at six months, with adverse drug reactions in only 7.5% of patients (5). Treatment persistence and patient satisfaction were high across the cohort.

Safety, Side Effects, and What to Watch For

Like all infliximab products, Zymfentra is a powerful immunosuppressant that requires respect and monitoring. Understanding the safety profile is essential for making an informed decision with your healthcare team.

Boxed Warnings Every Patient Should Know

Zymfentra carries the same boxed warnings as all infliximab products: risk of serious infections (including tuberculosis, invasive fungal infections, and opportunistic infections) and malignancy (including lymphoma) (6). These are not unique to the subcutaneous formulation - they apply to every form of infliximab. Before starting any infliximab product, your gastroenterologist should review your vaccination status, screen for tuberculosis, and test for hepatitis B.

Practical Things to Track Between Injections

The most common side effect specific to subcutaneous administration is injection site reactions - redness, swelling, or discomfort at the injection site. These tend to be mild and improve with time and proper technique.

Between injections, you should report fever, persistent or unusual infections, neurological symptoms (such as numbness, vision changes, or weakness), or signs of heart failure (such as new shortness of breath or swelling) to your gastroenterologist promptly. Therapeutic drug monitoring may still be useful in some patients to confirm adequate trough levels, even with the more stable pharmacokinetic profile of subcutaneous dosing.

Talking to Your Gastroenterologist About Switching or Starting

Whether you are considering a switch from IV infliximab or evaluating Zymfentra as part of a new treatment plan, having the right conversation with your gastroenterologist makes a difference. The treatment landscape for Crohn's continues to evolve - as we explored in our article on IL-23 inhibitors for Crohn's disease, newer biologic classes are also expanding the options available, so understanding where subcutaneous infliximab fits in your personal treatment strategy matters.

Questions worth asking include: What does the induction plan look like? When would I transition to subcutaneous injections? What should I do if I miss a dose? What symptoms should prompt me to call the office?

Insurance coverage, copay assistance programs, and pharmacy logistics often shape access as much as clinical considerations. Celltrion offers the Celltrion CARES program to help with financial assistance. For patients outside the United States, access pathways differ - in Europe, the product is marketed as Remsima SC and may have different coverage frameworks depending on your national healthcare system.

Discuss with your gastroenterologist whether combination therapy with an immunomodulator or monotherapy is most appropriate based on your risk profile. Plan for follow-up that may include fecal calprotectin monitoring, intestinal ultrasound or MR enterography, and periodic endoscopy as your gastroenterologist advises.

Frequently Asked Questions

Is subcutaneous infliximab as effective as IV infliximab for Crohn's disease?

The LIBERTY-CD trial demonstrated strong efficacy for subcutaneous infliximab as maintenance therapy, with 62.3% clinical remission at week 54 (1)(3). While the trial compared subcutaneous infliximab to placebo (not directly to IV maintenance), the pharmacokinetic profile actually shows more stable trough levels with subcutaneous dosing. Two-year extension data confirmed sustained remission in 63.5% of patients (2).

Can I start Zymfentra without IV infusion first?

No. The approved protocol requires completing IV infliximab induction at weeks 0, 2, and 6 before transitioning to subcutaneous maintenance injections (1)(6). Those initial infusions are necessary to build adequate drug levels quickly. After successful induction, you and your gastroenterologist can plan the transition to self-injection.

What does the injection feel like, and how long does it take?

Most patients describe the subcutaneous injection as a brief pinch lasting only seconds. The prefilled syringe or autoinjector is designed for ease of use. You remove it from the refrigerator, allow it to reach room temperature, clean the injection site (thigh or abdomen), and administer. The entire process takes just a few minutes, far shorter than an IV infusion session.

Does subcutaneous infliximab work regardless of where Crohn's disease is located?

A post hoc analysis of the LIBERTY-CD trial found consistent benefit across disease locations, with clinical remission rates of 60.95% for ileum-dominant disease and 66.95% for colon-dominant disease (4). This suggests the subcutaneous formulation is effective whether your Crohn's primarily affects your small intestine, colon, or both.

What are the most common side effects of Zymfentra?

The most common side effect specific to the subcutaneous route is injection site reactions, which are usually mild. Zymfentra also carries the same boxed warnings as all infliximab products regarding serious infections and malignancy (6). Your gastroenterologist will screen for tuberculosis and hepatitis B before starting treatment and monitor you throughout.

Is Zymfentra available outside the United States?

Yes. The subcutaneous infliximab formulation is marketed as Remsima SC in Europe and has been available there since before the US approval. Coverage and access pathways vary by country and healthcare system. If you are outside the US, speak with your gastroenterologist about local availability and what the transition process looks like in your region (5).

What should I ask my doctor before switching from IV to subcutaneous infliximab?

Key questions include: Am I a good candidate based on my current response and antibody status? What is the timing for switching after my last infusion? What do I do if I miss a scheduled injection? Are there financial assistance programs available? How will we monitor my response after the switch? Having this conversation ensures the transition is well planned and right for your situation.

References

1. Hanauer SB, Sands BE, Schreiber S, et al. Subcutaneous Infliximab (CT-P13 SC) as Maintenance Therapy for Inflammatory Bowel Disease: Two Randomized Phase 3 Trials (LIBERTY). Gastroenterology, 2024. Read study
2. Colombel JF, Sandborn WJ, Schreiber S, et al. Subcutaneous infliximab (CT-P13 SC) as maintenance therapy for Crohn's disease and ulcerative colitis: 2-year results from open-label extensions of two randomized controlled trials (LIBERTY). 2025. Read study
3. Healio Gastroenterology. FDA approves Zymfentra as first subcutaneous infliximab for ulcerative colitis, Crohn's. 2023. Read article
4. Healio Gastroenterology. Subcutaneous infliximab effective, regardless of Crohn's location. 2025. Read article
5. Safety and efficacy of transitioning inflammatory bowel disease patients from intravenous to subcutaneous infliximab: a single-center real-world experience. Annals of Gastroenterology, 2023. Read study
6. Celltrion USA. Zymfentra (infliximab-dyyb) Official Patient Information Site. 2024. Visit site