Teriparatide's label gained an allergic-reaction warning in August 2026, nearly six years after FDA removed its bone-cancer box

Why this note exists

Teriparatide is the first 34 amino acids of human parathyroid hormone, sold by prescription as a daily injection for osteoporosis.[2] Unlike most compounds in pepmg's compound pages, it is an FDA-approved drug with large randomized trials behind it, and its label has changed twice in a way that matters to anyone reading about it: a cancer warning that came off, and an allergy warning that went on.

This note sets out what changed, what the documents say, and what the human evidence shows. Every label and approval status below was checked on October 13, 2026.

The 2026 change

An FDA safety notice, then new labels for five drugs

FDA's August 3, 2026 approval letter to Eli Lilly refers to an April 20, 2026 letter "notifying you, under Section 505(o)(4) of the FD&C Act, of new safety information that we have determined should be included in the labeling for parathyroid hormone products. This information pertains to the risk of drug hypersensitivity reactions."[1] The revised Forteo label lists the change under Recent Major Changes, dated 08/2026.[2]

The new warning reads: "Hypersensitivity reactions, including anaphylaxis, angioedema, and urticaria, have been reported in patients treated with parathyroid hormone (PTH) analogs, including FORTEO." It tells prescribers to discontinue treatment if signs appear and to "discontinue FORTEO permanently in patients with a severe hypersensitivity reaction."[2] Patients are to be told to stop and "promptly seek medical attention."[2]

The risk itself was not new to the label. The July 2024 version already listed anaphylactic reactions, angioedema and urticaria among postmarketing reports and contraindicated Forteo in "patients with hypersensitivity to teriparatide or to any of its excipients."[3] What changed is its rank: it is now a numbered warning, first in the list. The contraindication was also narrowed, to patients with "a history of severe hypersensitivity."[2][3] Neither the approval letter nor the label gives a case count, and pepmg did not find the data behind FDA's determination.

Warning section numbers from each revised label.[2][6][7][8][9][10] Drugs@FDA records a labeling approval on August 3, 2026 for each of the five applications; pepmg read the approval letters for Forteo and Tymlos only.[11]

Tymlos's letter cites the same April 20 notice.[6] Abaloparatide is a different molecule from teriparatide, and Yorvipath treats low parathyroid hormone rather than osteoporosis, so the shared warning reflects a drug class, not one product.[7][10] Drugs@FDA also lists generic teriparatide from Teva, Apotex and Amphastar; pepmg did not check their current labels.[11] DailyMed published the revised Forteo label on August 19, 2026.[18]

The 2020 change

The bone-cancer box came off

Until 2020, Forteo carried a boxed warning, "Potential risk of osteosarcoma." It rested on rat studies: in Fischer 344 rats injected daily for up to two years, osteosarcoma "reached 40% to 50% in the high-dose groups," at exposures 3 to 60 times the human 20 mcg dose; no bone tumors were seen in untreated control rats or in a long-term monkey study.[2][4] The April 2020 label said use "for more than 2 years during a patient's lifetime is not recommended."[4]

The November 2020 label lists "Osteosarcoma Boxed Warning, Removed" among its recent major changes and rewrote the duration language.[5] The current label says use beyond two years "should only be considered if a patient remains at or has returned to having a high risk for fracture."[2] Osteosarcoma is still a warning: the label says it "has been reported in patients treated with FORTEO in the post marketing setting; however, an increased risk of osteosarcoma has not been observed in observational studies in humans," and that data beyond two years are limited.[2] It still advises avoiding the drug in people at higher baseline risk, including those with open growth plates, Paget's disease, bone metastases or prior skeletal radiation.[2]

The cancer evidence in humans

Surveillance found no excess, with wide uncertainty

The human data are observational, and the two published surveillance studies were run by RTI Health Solutions with a Lilly co-author; the registry paper states Lilly funding.[15][16] A cancer-registry study interviewed 1,173 adults diagnosed with osteosarcoma in the U.S. between 2003 and 2016, 24% of all such patients, and found three who had used teriparatide. Against 4.17 expected cases, the standardized incidence ratio was 0.72, with a 90% confidence interval of 0.20 to 1.86, an interval that includes nearly double the expected rate.[15] A voluntary Forteo patient registry linked 75,247 patients to 42 state cancer registries and found no cases, but its authors said conclusions were limited by "smaller than expected" follow-up.[16]

The label adds two U.S. claims-database studies with three and zero cases among 379,283 and 153,316 users, and says the results "suggest a similar risk" to comparators while calling for caution because the data sources "do not allow for complete measurement and control for confounders."[2] A 2022 review written by Lilly authors credits these large real-world studies with the 2020 removal of the box.[17] The same review notes that the phase 3 trials were stopped early because of the rat finding.[17]

The fracture evidence

Randomized trials in postmenopausal women

The pivotal trial. In the trial behind the approval, 1,637 postmenopausal women with prior vertebral fractures were randomized to 20 or 40 mcg of teriparatide or placebo daily, observed for a median of 21 months. New vertebral fractures occurred in 14% on placebo against 5% and 4% on the two doses, relative risks 0.35 and 0.31.[12] In the label's analysis of the 20 mcg dose, new vertebral fractures fell from 14.3% to 5.0%, an absolute reduction of 9.3 percentage points (95% CI 5.5 to 13.1), and nonvertebral fractures from 5.5% to 2.6%.[2] The vertebral fractures were seen on x-rays and, the label notes, "are not necessarily symptomatic."[2]

Against another drug. In the Lilly-funded VERO trial, 1,360 women with severe osteoporosis received daily teriparatide or weekly risedronate for 24 months. New vertebral fractures, the primary outcome, occurred in 5.4% against 12.0%, risk ratio 0.44 (95% CI 0.29 to 0.68). Clinical fractures were also lower; nonvertebral fractures were not significantly different, 4.0% against 6.1%, p = 0.10.[13]

Glucocorticoid users. In an 18-month trial of 428 adults taking steroids, teriparatide raised lumbar spine bone density more than alendronate, 7.2% against 3.4%, the primary outcome. Fewer new vertebral fractures, 0.6% against 6.1%, was a secondary finding; nonvertebral fractures were similar.[14]

From the abstracts and the current Forteo label.[2][12][13][14][15] Full texts were not read.

Three things this note is not saying

It is not saying allergic reactions to teriparatide are common. The label lists arthralgia, pain and nausea as the most common adverse reactions, and gives no frequency for hypersensitivity, which comes from voluntary reports.[2]

It is not saying teriparatide has been shown not to cause osteosarcoma. The surveillance studies found no excess, but cases were few and the confidence intervals wide.[15][16]

It is not saying anything about material sold outside pharmacies. The label, the trials and the surveillance studies describe the FDA-approved products, used at 20 mcg once daily under the skin; the label says Forteo "is not approved for intravenous or intramuscular use."[2] This note reports evidence and regulatory status, not medical advice.

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