What Entera Said
Entera Bio released its first quarter 2026 financial results on May 11 with a regulatory update that matters beyond its share price. The company says it has submitted what it calls a "streamlined" Phase 3 protocol to the FDA for EB613, an oral anabolic peptide tablet for postmenopausal osteoporosis, and that FDA feedback is expected imminently. If the protocol clears, Entera plans to start a roughly 750-patient Phase 3 trial measuring change in total hip bone mineral density at twelve months as the primary endpoint.
That sentence carries a lot of weight. Anabolic bone drugs — the kind that build new bone rather than just slow resorption — have, since FDA approval of teriparatide in 2002, been delivered as daily subcutaneous injections. EB613 would be the first oral version. Same biological target, same anabolic class, swallowed instead of injected. That is the entire pitch, and the entire scientific bet.
Key Facts
- Company: Entera Bio (NASDAQ: ENTX), Jerusalem-based oral peptide platform
- Lead asset: EB613, oral parathyroid hormone (PTH 1-34) tablet for postmenopausal osteoporosis
- Regulatory status (May 11, 2026): Phase 3 protocol submitted to FDA under 505(b)(2) IND; feedback expected imminently
- Planned Phase 3 design: Multinational, randomized, double-blind, placebo-controlled; ~750 postmenopausal women; primary endpoint % change in total hip BMD at month 12
- Extension synopsis: 24 months of EB613 monotherapy or 12 months EB613 then 12 months standard antiresorptive
- Reference comparator: Forteo (teriparatide, 20 mcg subcutaneous daily)
- Phase 1 bridging study: Single-tablet vs multi-tablet EB613 vs Forteo PK/safety completed January 2026; single-tablet selected for Phase 3
- Pipeline: EB612 (oral long-acting PTH for hypoparathyroidism, IND planned late 2026, 50/50 OPKO partnership); EB618 (oral oxyntomodulin, dual GLP-1/glucagon, preclinical)
- Scientific venue: Incremental data submitted to ENDO2026 and ASBMR 2026
Why Oral Peptides Are Hard
Peptides are short chains of amino acids, and the human gut is built to destroy them. Stomach acid denatures most peptide structures within minutes. Pancreatic and brush-border proteases cleave whatever survives. What is left has to cross the intestinal epithelium — a tight monolayer of cells stitched together by tight junctions — and reach the portal circulation in enough quantity to do something pharmacologically useful. For a 34-amino-acid molecule like PTH 1-34, the oral bioavailability problem has historically been a wall.
Two oral peptide drugs have crossed it in commercial form. Semaglutide tablets (Rybelsus, Novo Nordisk, 2019) use a permeation enhancer called SNAC that locally alkalinizes the stomach to protect the peptide and assists transcellular absorption. Oral octreotide (Mycapssa, Chiasma, 2020) uses a transient permeation enhancer called TPE. Both achieve oral bioavailability in the low single digits, which is enough only because their respective receptors are tolerant of low and variable plasma exposure.
EB613 is Entera's third platform: a proprietary excipient stack designed to deliver larger, more fragile peptides than SNAC can manage. The 2022 Phase 2 readout in postmenopausal women with low BMD showed a dose-dependent rise in lumbar spine BMD comparable in direction to teriparatide, alongside the bone formation marker P1NP rising and resorption marker CTX dropping — the biochemical signature of anabolic bone activity. That was the proof-of-concept that justified building toward Phase 3.
What the FDA Is Actually Being Asked to Bless
The protocol Entera has put in front of the FDA is a 505(b)(2) filing. That regulatory pathway lets a sponsor reference safety and efficacy data from a previously approved product — in this case, the twenty-plus years of clinical and post-marketing data on injectable teriparatide — instead of rebuilding the entire dossier from scratch. The agency does not have to be convinced that PTH 1-34 builds bone. It has to be convinced that EB613 delivers enough PTH 1-34, with a clean enough safety profile, to claim the same effect.
That is why the bridging study Entera completed in January 2026 matters. Phase 1 compared the new single-tablet EB613 formulation against the prior multi-tablet formulation and against Forteo as the active control. The company has not yet released the full PK numbers, but the fact that it is advancing the single-tablet into Phase 3 suggests the exposure curves were close enough to Forteo to support a non-inferiority framing. Patient acceptability matters here: a single tablet once a day is a different adherence story than three tablets, and adherence is one of the well-documented failure points of injectable teriparatide in clinical practice.
The Phase 3 primary endpoint — percent change in total hip BMD at month 12 — is itself an FDA-agreed shortcut. Hip BMD change has been accepted as a registration endpoint for osteoporosis drugs for years; fracture endpoints require larger trials and longer follow-up. For Entera and for any sponsor of an anabolic bone drug, the BMD endpoint is the difference between a feasible Phase 3 and an infeasible one.
Why This Matters Beyond Entera
An oral anabolic bone tablet, if approved, reshapes the osteoporosis treatment funnel. Today the practical sequence runs like this. Patients with low BMD start on calcium, vitamin D, and lifestyle modification. Patients with confirmed osteoporosis go to bisphosphonates — alendronate, risedronate, zoledronic acid. Patients who fracture on bisphosphonates, or whose BMD continues to fall, may move to denosumab. Patients with severe disease or with glucocorticoid-induced osteoporosis qualify for two years of injectable anabolic therapy: teriparatide, abaloparatide, or romosozumab. The injection step is where adherence collapses. Many eligible patients never start. Many who start stop before the two-year course is complete.
EB613 is positioned exactly there. It is not trying to displace bisphosphonates as first-line therapy. It is trying to be the anabolic agent that more patients actually take. If a daily tablet produces hip BMD gains comparable to teriparatide injections, the prescribing calculus changes. So does the patient calculus. Self-injecting a recombinant hormone every day, for two years, with refrigerated storage and an autoinjector pen, is a meaningful behavioral ask. Swallowing a pill is not.
This is also the second platform validation event for Entera's oral peptide delivery system in roughly eighteen months. The same excipient approach is being applied to EB612, the company's long-acting oral PTH program for hypoparathyroidism — a different indication, same hormone backbone, different release profile. The IND for EB612 is planned for late 2026 under an expanded 50/50 partnership with OPKO Health. The third asset, EB618, is an oral oxyntomodulin program in preclinical development that pivots the platform away from bone and toward metabolic disease.
The GLP-1 Shadow Over Oral Peptides
Any peptide story in 2026 sits inside a much larger GLP-1 story. Oral semaglutide tablets launched in the U.S. on a fresh cardiovascular indication in April. The FDA's compounding regulatory landscape has been rewriting itself around GLP-1 supply through the first half of the year. The bulk drug compounding list, the 503B exclusion list, the warning letters — almost all of it has been GLP-1 driven.
EB618 sits squarely in that shadow. Oxyntomodulin is a 37-amino-acid gut peptide that activates both GLP-1 and glucagon receptors. The dual mechanism is attractive: GLP-1 agonism for satiety and glycemic control, glucagon receptor activity for energy expenditure and potentially better preservation of lean mass than pure GLP-1 agonism delivers. Oxyntomodulin has been studied as an injectable for years; an oral version would compete in the same crowded oral GLP-1 tablet space that Novo Nordisk has been defining with Rybelsus.
EB613 and EB612 are in a different competitive space. There is no marketed oral PTH product. There is no late-stage oral PTH competitor in the public clinical pipeline. The market opportunity is the entire injectable anabolic osteoporosis market plus the patients who never start anabolic therapy because they refuse injections. CDC data put roughly ten million Americans with osteoporosis, with adult prevalence rising as the population ages. Of those eligible for anabolic therapy, the conservative estimate is that under twenty percent actually receive it.
What Can Go Wrong
The honest list. PK variability is the first risk. Oral peptide formulations are sensitive to food, gut pH, motility, and inter-patient differences in transit time. A drug that hits the target exposure in fasted lab settings may not hit it in patients who took their tablet with coffee or with a heavy meal. Entera will need consistent exposure across enrolled subjects to claim non-inferiority to Forteo. Variability is the historical Achilles heel of oral peptide drug development.
The second risk is the rodent osteosarcoma signal that has shadowed PTH 1-34 since the original Forteo Phase 3. FDA removed the boxed warning in 2020 after twenty years of human surveillance failed to surface a signal, but the residual label language still flags caution in patients at baseline osteosarcoma risk. EB613 inherits that label issue. It does not change it.
The third risk is commercial. Even if the trial succeeds and the drug is approved, payer coverage in osteoporosis is constrained. Bisphosphonates are generic and cheap. Anabolic agents are expensive. An oral anabolic agent would likely be priced in the range of injectable teriparatide, and the field has watched payer step-edit policies push patients through bisphosphonates first regardless of fracture risk. Adherence advantages help, but they are not a payer argument by themselves.
The fourth risk is timing. With FDA feedback "imminent" but unannounced as of this writing, the trial start date is not yet anchored. A standard Phase 3 trial with a 12-month primary endpoint and a 24-month extension realistically reads out between mid-2028 and 2029. The FDA submission window after that puts a possible approval in 2029 or 2030. Entera has stated a roughly three-year runway. The cash arithmetic on a company this size, with a single late-stage asset, is real.
What This Means for Patients and Clinicians Today
Nothing changes in standard of care this week. EB613 is investigational. It is not available outside a clinical trial. Patients on injectable teriparatide, abaloparatide, or romosozumab should continue their prescribed therapy. Patients eligible for anabolic therapy but resistant to injection are still in the same place they were yesterday.
What changes, slightly, is the conversation a year from now. If Entera's Phase 3 starts in late 2026 or early 2027 as the company is planning, sites will begin enrolling postmenopausal women with osteoporosis. Patients who have been counseled toward anabolic therapy but declined the injection burden are the natural enrollee population. Clinicians treating osteoporosis should be aware the trial is coming. The company has not yet posted site lists; trial registry information will appear on ClinicalTrials.gov when enrollment opens.
For the broader oral peptide field, the EB613 readout will be one of the cleanest tests in years of whether the platform approach — excipients plus tablet engineering — can deliver therapeutic exposure of a peptide drug that previously required injection. A positive result is platform validation for EB612 and EB618 and for the dozen smaller programs across the industry pursuing the same goal. A negative result is the opposite signal and pushes oral peptides back toward narrow indications where low-and-variable bioavailability is tolerable.
This is not a binary yet. It is an interaction with the FDA, a planned trial design, and a company in line for a Phase 3 start. The next concrete milestone is the FDA's response to the submitted protocol, which the company has framed as imminent. After that, trial start, enrollment pace, and the eventual hip BMD number at month 12 are the markers worth watching.
Frequently Asked Questions
Is EB613 the same drug as Forteo?
The active molecule is the same — recombinant human PTH 1-34, also called teriparatide. The difference is the delivery system. Forteo is a subcutaneous injection delivered by a prefilled pen, once daily. EB613 is a tablet built around a proprietary excipient stack designed to protect the peptide through the stomach and assist its absorption across the intestinal wall. The biology of the drug is well established. The novelty is the tablet.
When could EB613 be available?
The earliest plausible window is 2029 or 2030, contingent on a successful Phase 3, FDA review, and manufacturing scale-up. The Phase 3 primary endpoint reads out at month 12 after the last patient is randomized, which means a trial starting in late 2026 or early 2027 would read out in late 2027 or 2028. After that, the company has to file a 505(b)(2) New Drug Application, which the FDA reviews on a standard ten- or twelve-month clock. Any delay at any step pushes the date out.
What is a 505(b)(2) filing?
It is a section of the U.S. Food, Drug, and Cosmetic Act that lets a sponsor reference safety and efficacy data already submitted to the FDA by another applicant. In Entera's case, the agency has more than two decades of teriparatide data on file. A 505(b)(2) NDA for EB613 does not have to reprove that PTH 1-34 builds bone. It has to show that the EB613 tablet delivers the molecule with comparable exposure and a clean safety profile. The pathway is faster and cheaper than a full NDA and is the standard route for new formulations of approved active ingredients.
Why is the primary endpoint hip BMD instead of fractures?
Fracture endpoints require very large trials and long follow-up. To detect a fracture rate reduction at conventional statistical thresholds, sponsors need thousands of patients tracked for two years or more. BMD endpoints are a well-validated surrogate. The FDA has accepted BMD change as a registration endpoint for osteoporosis drugs since the 1990s based on the consistent correlation between BMD gain and fracture risk reduction across drug classes. For an anabolic agent, hip BMD is the more demanding site than spine and is the one regulators favor.
How does EB618 fit with the rest of the oral GLP-1 market?
EB618 is preclinical, which means it is several years behind the current oral GLP-1 leaders. Oxyntomodulin's appeal is its dual agonism — GLP-1 plus glucagon — which differentiates it mechanistically from pure GLP-1 agents. If Entera's tablet platform can deliver oxyntomodulin at therapeutic exposure, the program would compete in the obesity and metabolic dysfunction-associated steatohepatitis space rather than in the broader GLP-1 weight-loss market currently dominated by injectable semaglutide and tirzepatide. The strategic logic is platform reuse, not first-mover advantage.
Is there any other oral PTH drug in development?
There is no other late-stage oral PTH 1-34 program publicly disclosed. A few companies have explored alternative delivery routes for PTH — transdermal patches, intranasal sprays — with mixed results. None has reached Phase 3 status. EB613 is the first program to take an oral PTH formulation into a Phase 3 protocol negotiation with the FDA.
What about EB612 and hypoparathyroidism?
Hypoparathyroidism is a chronic condition in which the parathyroid glands fail to produce sufficient PTH, leading to hypocalcemia and hyperphosphatemia. Standard care involves calcium and active vitamin D, which often fail to control symptoms. Recombinant PTH replacement therapy exists as a daily injection (Natpara, withdrawn in 2024 due to manufacturing issues) and as palopegteriparatide (Yorvipath, approved 2024). An oral long-acting PTH tablet, if proven, would be the first oral option in this orphan indication. The IND is planned for late 2026.
Sources
- Entera Announces First Quarter 2026 Financial Results and Updates Across its Oral Peptide Programs — BioSpace press release, May 11, 2026 (primary source for FDA submission, Phase 3 design, and pipeline status)
- FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize — U.S. Food and Drug Administration, 2026
- FDA considers adding a dozen peptides to its bulk drug compounding list — Regulatory Affairs Professionals Society, 2026
- Effect of parathyroid hormone (1-34) on fractures and bone mineral density in postmenopausal women with osteoporosis — Neer et al., New England Journal of Medicine, 2001 (foundational teriparatide Phase 3)
- Oral parathyroid hormone (PTH 1-34) tablet in postmenopausal women with low bone mineral density: a Phase 2 dose-ranging study — PubMed (EB613 Phase 2 data)
- FDA guidance: Applications covered by section 505(b)(2) — U.S. Food and Drug Administration
- Osteoporosis facts and statistics — International Osteoporosis Foundation
- ENDO 2026 Scientific Sessions — Endocrine Society Annual Meeting (venue for Entera data submissions)
- American Society for Bone and Mineral Research — ASBMR (venue for Entera data submissions)
- SNAC (Sodium N-[8-(2-hydroxybenzoyl)amino]caprylate) — PubChem entry on the Rybelsus permeation enhancer
Sources & References
- FDA PCAC Meeting Announcement (July 23-24, 2026)
- PBS: FDA to Weigh Easing Limits on Peptides Favored by RFK Jr.
- BioPharma Dive: FDA Peptides RFK Advisory Committee Restrictions
- RAPS: FDA Considers Adding a Dozen Peptides to Bulk Drug List
- Ars Technica: RFK Jr. Forces FDA to Reconsider 12 Peptides
- ProPublica: Peptide Safety Investigation
- New York Times: Peptide Ban FDA RFK Jr.
- SSRP Institute: FDA Announces Change in Status of 12 Peptides
- CNBC: RFK Jr. Peptides Hims Hers GLP-1
- USA Today: RFK Jr. FDA Peptides Explainer
