Understanding Your PCT Search Report and What Happens When You Enter the US

A plain-language guide for patent applicants pursuing international protection.

PUBLISHED

June 20, 2026

AUTHOR

Sam Redford, PhD

Patent Partner

Sam previously drafted and filed patents at Mintz and Morrison Foerster. He received his PhD in immunology from UCSD on the interactions between immune cells and lipid metabolism during chronic parasitic infection.

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Introduction.

If you have filed a PCT (Patent Cooperation Treaty) application and will enter national phase in the US, you will receive two types of written assessments at different stages of your patent journey: the International Search Report (ISR) and, after you enter the US national phase, one or more Office Actions from the United States Patent and Trademark Office (USPTO). These documents serve very different purposes, carry different legal weight, and require very different responses from you and your attorneys.

This article explains what each document is, how they differ, what types of issues are most commonly raised, and the strategies we use to address them on your behalf.

Part 1: The International Search Report (ISR).

What Is the ISR?

When you file a PCT application, an International Searching Authority (ISA) — typically the USPTO, the European Patent Office (EPO), or the Japan Patent Office (JPO) — conducts a search of the existing body of published literature (called “prior art”) and issues an International Search Report along with a Written Opinion. This typically occurs within 16–18 months of your earliest priority date.

The ISR identifies prior art documents that the ISA considers relevant to the novelty and inventive step of your claims. The accompanying Written Opinion sets out the ISA’s preliminary view on whether your claims appear to be novel, inventive, and industrially applicable.

Key Point: The ISR Is Not Binding.

This is one of the most important things to understand: the ISR and Written Opinion are advisory only. They do not reject your claims. They do not grant or refuse your patent. Each national patent office, including the USPTO, conducts its own independent examination when you enter the national phase and is not bound by the ISA’s conclusions.

That said, the ISR is far from meaningless. It is a valuable early signal. A favorable Written Opinion (one concluding that your claims appear novel and inventive) suggests the path ahead will be smoother. An unfavorable opinion, particularly one citing close prior art, gives us the opportunity to consider claim amendments before national phase entry, potentially saving time and cost downstream.

Should We Respond to the ISR?

A response is not required. However, two optional mechanisms exist:

Article 19 Amendments: You may amend the claims of your PCT application in response to the ISR. This is a one-time opportunity and the amendments are filed directly with the International Bureau. Amendments are often made to sharpen claim distinctions over the cited prior art before national phase entry.
Article 34 Amendments (Demand): If you file a “Demand” for international preliminary examination, a second-stage examination is conducted by the International Preliminary Examining Authority (IPEA), and you may file Article 34 amendments during that process. This extends the period before national phase entry decisions must be made and can produce a more favorable International Preliminary Report on Patentability (IPRP).

Whether to file amendments at the PCT stage is a strategic decision we will discuss with you based on the strength of the cited art and your commercial priorities.

Part 2: The US National Phase Office Action.

What Happens When You Enter the US National Phase?

When you elect to pursue patent protection in the United States, you file a US national phase application under 35 U.S.C. § 371, typically by the 30-month deadline from your earliest priority date. At this point, your application is assigned to a USPTO examiner who will conduct a fresh, independent examination under US patent law.

The examiner will search the prior art, review your claims, and issue a written Office Action setting out any objections or rejections. This is a formal legal document, and an inadequate or untimely response can result in abandonment of your application.

How Is a US Office Action Different from the ISR?

The table below summarizes the key differences:

Feature	International Search Report (ISR)	US Office Action (National Phase)
Issued by	International Searching Authority (ISA) — typically the USPTO, EPO, or JPO	USPTO examiner assigned to the US national phase application
Legal effect	Non-binding advisory opinion — does not reject or allow claims	Formal legal action — rejections must be overcome or the application goes abandoned
Response required?	No mandatory response; applicant may file a voluntary Demand for international preliminary examination (IPEA)	Yes — response due within 3 months (extendable to 6 months with fees)
Timing	Issued ~16–18 months from priority date, before national phase entry	Issued after national phase entry; first action typically 18–30 months from priority
Claim amendments	Article 19 amendments may be filed in response to the ISR; Article 34 amendments available if Demand filed	Amendments may be filed with response; after Final Office Action, amendments are restricted without an RCE
Scope of review	Novelty (Art. 33(2)), inventive step (Art. 33(3)), and industrial applicability (Art. 33(4)) under PCT standards	Novelty (§ 102), non-obviousness (§ 103), subject matter eligibility (§ 101), and written description/enablement (§ 112)
Strategic value	Early signal of patentability; informs decisions on which countries to enter national phase and whether to amend claims before entry	Determines the actual scope of claims that will be granted in the US; each action shapes the final patent

How Many Office Actions Should We Expect?

Most US patent applications receive at least one Office Action before allowance. In biotechnology and antibody-related cases, two to four rounds of examination are common, and it is not unusual to file a Request for Continued Examination (RCE) to continue prosecution after a Final Office Action.

Part 3: Common Rejections and How We Address Them.

The following table summarizes the most common types of rejections encountered during US national phase prosecution, along with the strategies we typically use to overcome them.

Rejection Type	What the Examiner Is Arguing	Common Response Strategies
Lack of Novelty 35 U.S.C. § 102	The examiner has identified a single prior art reference that discloses every element of one or more claims.	Distinguish the claims from the cited reference by identifying claim elements not disclosed or taught by the reference. Amend claims to add structural or functional limitations not present in the prior art. Argue that the reference does not anticipate because a key element is missing, modified, or used in a different context.
Obviousness 35 U.S.C. § 103	The examiner argues that the claimed invention would have been obvious to a person of ordinary skill in the art at the time of filing, based on a combination of prior art references.	Attack the examiner’s rationale for combining references: identify the absence of motivation to combine, or show the combination would require undue experimentation or yield a different result. Submit objective indicia of non-obviousness (secondary considerations): unexpected results, commercial success, long-felt need, failure of others, or copying by competitors. In biotech cases, submit experimental data via a § 1.132 declaration demonstrating unexpected results or efficacy. Amend claims to highlight structural features not present in or suggested by the combined references.
Written Description 35 U.S.C. § 112(a)	The examiner argues that the specification does not adequately describe the full scope of the claimed invention.	Submit a § 1.132 declaration from an expert or inventor demonstrating that the structural features recited in the claims are representative of the genus and predictive of function. Narrow claims to a tighter genus or specific species (e.g. individual antibodies) that are fully supported by working examples.
Enablement 35 U.S.C. § 112(a)	The examiner argues that even if the invention is described, a person of ordinary skill in the art could not make and use the full scope of the claimed invention without undue experimentation.	Address the quantity of experimentation needed, amount of direction provided, presence of working examples, nature of the invention, skill level in the art, predictability of the technology. Submit data or declarations showing that the claimed methods are routine and that the full scope can be practiced without undue experimentation. Narrow claims to the embodiments that are fully enabled in the specification. Distinguish from Amgen v. Sanofi by showing the claims are not a purely functional genus but are structurally defined with enabling disclosure.
Patent Eligibility 35 U.S.C. § 101	The examiner applies the Alice/Mayo framework to argue that the claims are directed to a natural phenomenon, natural product, law of nature, or abstract idea without adding significantly more.	For biological compositions claims: argue the composition is not a naturally occurring product; it is a specific man-made molecule with a defined sequence not found in nature. For method claims: demonstrate that the claim elements, taken individually and as an ordered combination, amount to significantly more than the judicial exception. Amend method claims to require a specific treatment step or concrete application, avoiding purely correlative or diagnostic language.
Definiteness 35 U.S.C. § 112(b)	The examiner argues that the claims do not particularly point out and distinctly claim the subject matter of the invention, or that a claim term is indefinite.	Amend the claim term to use language that is clearly defined in the specification. Argue that the term has a well-understood meaning in the art and cite technical literature or treatises supporting that meaning.

Part 4: The Relationship Between the ISR and US Prosecution.

Prior Art Cited in the ISR Often Reappears in US Office Actions.

While the USPTO examiner is not bound by the ISA’s search, the prior art references identified in the ISR frequently appear in US Office Actions as well. This is because the same body of published literature is searched. A significant advantage of the PCT route is therefore the advance notice it provides: we can study the cited references before national phase entry and develop arguments and, where appropriate, claim amendments in anticipation of the USPTO’s likely rejections.

Using the ISR to Inform National Phase Entry Decisions.

The ISR is also an important tool for deciding whether to enter the national phase in a given country at all. Pursuing patent protection in multiple jurisdictions is expensive. If the ISR identifies highly relevant prior art that significantly narrows the likely scope of your patent, that information may affect the commercial calculus of seeking protection in certain markets.

A Favorable IPRP/ISR Can Accelerate US Prosecution.

If you filed a Demand and received a favorable International Preliminary Report on Patentability (IPRP) — one concluding that your claims are novel, inventive, and industrially applicable — this can be submitted to the USPTO examiner as part of an interview or response to encourage allowance. While not binding, a favorable IPRP from a respected ISA carries persuasive weight and can shorten prosecution. Additionally, a favorable IPRP/ISR can be used as the basis for requesting to use the Patent Prosecution Highway in the US to speed up prosecution.

Part 5: Practical Guidance for Applicants.

Key Takeaways
Review Early	When you receive your ISR and Written Opinion, review them to consider voluntary amendments and to plan your national phase strategy before deadlines arrive.
Preserve Data	For biotechnology and antibody inventions, robust experimental data is your most powerful tool for overcoming written description, enablement, and obviousness rejections.
Budget Realistically	US patent prosecution for complex biotech inventions typically requires 3–5 years and multiple Office Action responses. We will provide budget estimates at each stage so there are no surprises.
Act Promptly	Office Action response deadlines are strict. Missing a deadline without an extension on file will result in abandonment of your application.

This article is intended as a general educational resource and does not constitute legal advice specific to your matter. Please consult your attorney/agent for guidance tailored to your application.