Isomab has presented a systematic review aimed at addressing one of the longstanding objections to therapeutic angiogenesis: whether deliberately encouraging new blood-vessel growth in patients with ischemic cardiovascular disease could also increase cancer or retinal disease. The analysis covered 11 clinical studies conducted between 2002 and 2024 involving 636 patients with angina or peripheral artery disease. Of those patients, 441 received pro-angiogenic therapies and 195 received placebo, with follow-up lasting between two and 12 years. Mean malignancy incidence was 0.84 per 100 patient-years in the angiogenesis groups and 0.72 per 100 patient-years under placebo, both below a reported age-matched population rate of 1.0 per 100 patient-years.
The finding is relevant to Isomab because the company is preparing ISM-001, a first-in-class antibody targeting the anti-angiogenic VEGF-A165b isoform, for first-in-human development. Yet the distinction between the systematic review and ISM-001 itself is critical. The 636 patients were treated in historical studies of earlier pro-angiogenic approaches, not with ISM-001. The review may weaken the argument that therapeutic angiogenesis as a whole inevitably creates excess malignancy, but it does not establish the safety or efficacy of Isomab’s investigational antibody.
Why have cancer concerns followed therapeutic angiogenesis for decades?
Tumors require blood vessels to grow beyond a small size. Oncology has therefore spent decades developing anti-angiogenic therapies intended to suppress vascular endothelial growth factor, or VEGF, signaling and starve malignant tissue of the blood supply needed for expansion.
Cardiovascular regenerative therapy proposes something that appears to move in the opposite direction. In a heart with severely restricted coronary blood flow, researchers would like to encourage collateral vessels to grow around blocked arteries and supply ischemic muscle.
That immediately creates an intuitive safety concern. If medicine promotes blood-vessel growth in the heart, could an undiagnosed tumor also use the same signal to grow faster?
Similar questions apply to the eye, where abnormal vascular proliferation can contribute to retinal disease.
Those concerns helped slow development of older therapeutic-angiogenesis programs even when early studies suggested potential improvements in blood flow or symptoms.
What did the 11-study systematic review actually find?
Isomab’s review pooled long-term safety information from studies performed between 2002 and 2024 in patients with angina or peripheral artery disease. The 11 studies included 636 participants, with 441 receiving a pro-angiogenic intervention and 195 receiving placebo. Follow-up ranged from two years to as long as 12 years.
Mean malignancy incidence was 0.84 events per 100 patient-years with angiogenic treatment versus 0.72 with placebo. Both were below the reported age-matched background rate of approximately one per 100 patient-years. Retinal adverse events were also rare and below the age-matched population reference cited by the investigators.
The absence of a clear excess is reassuring because the follow-up extended far beyond the immediate treatment period in some studies. A cancer-promoting effect might plausibly require years rather than weeks to become visible.
However, 636 patients still represent a relatively small safety database for detecting uncommon malignancies, and the treatments, doses and populations varied among studies.
The conclusion should therefore be “no increased signal was detected,” not “angiogenic therapy has been proven incapable of increasing cancer risk.”
Why is the historical review relevant if those patients did not receive ISM-001?
The review addresses a mechanism-level concern. If decades of attempts to stimulate blood-vessel growth had produced a consistently higher cancer rate, any new angiogenic program would begin with a substantial conceptual safety problem regardless of its precise molecule.
Finding no clear signal gives Isomab more confidence that promoting vascular growth in ischemic disease is not inherently unacceptable.
But ISM-001’s mechanism is different from directly giving a growth factor. The antibody is designed to neutralize VEGF-A165b, an isoform of VEGF-A that inhibits angiogenesis. Instead of adding more pro-growth signaling, Isomab wants to remove an endogenous brake that becomes pathologically elevated in cardiovascular disease.
That difference could theoretically produce more localized or physiologically regulated vessel growth, but it could also create risks not captured by historical growth-factor programs.
ISM-001 therefore requires its own toxicology and human safety data regardless of how reassuring the systematic review appears.
What exactly is VEGF-A165b and why would blocking it grow new vessels?
VEGF-A is commonly discussed as if it were one molecule, but alternative RNA splicing can produce different protein isoforms with different biological effects. VEGF-A165b is an anti-angiogenic splice variant that can inhibit the vessel-growth activity associated with conventional pro-angiogenic VEGF signaling.
Isomab’s scientific founders have argued that VEGF-A165b becomes an important brake on collateral-vessel development in ischemic cardiovascular disease. ISM-001 is a humanized antibody designed to bind and neutralize that isoform, allowing the body’s remaining pro-angiogenic signals to function more effectively.
The company describes the intended result as enabling a “biological bypass.” Instead of a surgeon physically connecting another vessel around a coronary obstruction, new or remodeled collateral vessels would theoretically carry blood into underperfused heart muscle.
That phrase should not be confused with evidence that ISM-001 already accomplishes this in people. The program remains preclinical and is moving toward first-in-human testing.
Why could chronic refractory angina be a logical first indication?
Angina occurs when the heart muscle demands more oxygen than restricted coronary blood flow can provide, often producing exertional chest discomfort. Many patients can be treated with medicines, percutaneous coronary intervention or coronary bypass surgery.
A difficult subgroup remains symptomatic despite optimal treatment and may no longer have anatomy suitable for additional conventional revascularization. These patients can experience repeated chest pain and major limitations on exercise and quality of life even when immediate mortality risk is not the only clinical issue.
A therapy capable of promoting functional collateral circulation could theoretically improve blood supply without placing another stent or performing another bypass.
Isomab currently describes chronic stable or refractory angina as a major target for ISM-001’s initial development.
The clinical challenge will be proving that newly formed vessels actually improve myocardial perfusion and symptoms rather than merely creating anatomical changes visible on imaging.
Could growing vessels really modify the disease rather than just relieve symptoms?
That is the core promise of therapeutic angiogenesis. Conventional anti-anginal drugs can reduce heart rate, oxygen demand or symptoms, but they do not necessarily create new pathways for blood to reach ischemic tissue.
If ISM-001 successfully restores collateral-vessel growth, it could theoretically alter the supply side of the problem.
Researchers would need objective evidence such as myocardial perfusion imaging, exercise capacity or physiological measures demonstrating that blood flow genuinely improved. Patient-reported angina frequency and quality of life would also matter because the ultimate purpose is to allow people to function more normally.
A first-in-human trial will probably focus initially on safety and biological activity rather than proving reductions in cardiovascular death or myocardial infarction.
Large outcomes studies would be required before making claims that the therapy prevents major cardiovascular events.
Why did earlier therapeutic-angiogenesis approaches struggle?
The field has tested recombinant growth factors, gene therapies and other methods intended to increase VEGF or fibroblast growth-factor signaling. Some generated biological activity, but clinical results were inconsistent and practical delivery was difficult.
Simply adding a growth factor can produce transient exposure rather than sustained physiological remodeling. High systemic concentrations can also raise safety concerns, while locally administered treatment may not reach enough tissue.
Another challenge is that ischemic disease contains several brakes on vessel growth. Increasing one positive signal may accomplish little if strong endogenous inhibitory pathways remain active.
Isomab’s thesis is that targeting VEGF-A165b attacks one of those brakes instead of trying to overwhelm it with additional growth factor.
Whether that produces a more effective therapeutic window remains entirely unproven in humans.
What are the limitations of the new 636-patient safety analysis?
The first limitation is heterogeneity. Eleven studies conducted over more than 20 years inevitably used different interventions, doses, follow-up methods and patient populations.
Second, cancer and retinal events were not necessarily the primary endpoints of those trials. Retrospective long-term safety collection can miss events if surveillance methods differ.
Third, the placebo population contained only 195 patients, making numerical comparisons vulnerable to a few events.
Fourth, a mean malignancy rate below an age-matched population does not prove treatment protects against cancer or even that the study population is directly comparable with the reference population.
Finally, none of the 636 patients received ISM-001.
The review is consequently useful for asking whether the class-level fear is supported by historical evidence. It cannot replace the prospective safety database that Isomab must build for its own drug.
Where is ISM-001 in development today?
Isomab has been conducting preclinical and IND-enabling development, including manufacturing work intended to supply future clinical studies. The company previously entered collaborations with organizations including Catalent and Pfizer Ignite to support development activities.
The September update says Isomab is preparing ISM-001 for first-in-human studies in patients with chronic angina who remain symptomatic despite existing treatment.
No human participant has yet demonstrated improved perfusion, fewer angina episodes or clinical benefit from ISM-001.
That makes this an enabling evidence story rather than an efficacy story.
Could ISM-001 eventually matter beyond coronary artery disease?
Potentially. The same fundamental problem of inadequate blood supply occurs in peripheral artery disease and chronic limb-threatening ischemia, where severely reduced circulation can contribute to pain, non-healing ulcers and amputation risk.
Earlier Isomab development materials emphasized peripheral arterial disease, particularly in patients with diabetes, and the company’s collaborations have included preclinical work in that area.
If neutralizing VEGF-A165b restores useful collateral circulation, the mechanism could theoretically apply wherever ischemic tissue fails to develop sufficient compensatory vessels.
Each indication would still require specific clinical evidence because the anatomy, comorbidities and endpoints differ substantially between the heart and lower limbs.
What should cardiologists watch when ISM-001 reaches the clinic?
Safety comes first. Investigators need to monitor malignancy, retinal effects, edema, vascular abnormalities and other consequences of altering VEGF biology.
Pharmacodynamics come next. Researchers need evidence that the antibody actually neutralizes its intended isoform and changes vascular behavior at clinically tolerable exposures.
Then comes the hardest question: whether collateral vessels grow in a way that meaningfully improves perfusion.
The new systematic review makes that experiment easier to justify because more than two decades of historical angiogenic trials did not reveal the excess malignancy or retinal signal long feared by the field.
It does not guarantee that Isomab’s own molecule will be safe. Nor does it establish that therapeutic angiogenesis will finally work after numerous earlier disappointments.
What it does is narrow the uncertainty. The central question can increasingly shift from “will encouraging vessel growth inevitably cause cancer?” toward the scientifically more interesting question: “can physicians restore enough controlled collateral circulation to help an ischemic heart without creating unacceptable new risk?”
